I'm experiencing the same thing on Dell XPS 15 9560 with:
kernel-4.18.8-200.fc28.x86_64
linux-firmware-20180815-86.gitf1b95fe5.fc28.noarch

The errors in the logs look like:
Sep 21 21:32:08 toronto kernel: ath10k_warn: 151 callbacks suppressed
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:08 toronto kernel: ath10k_pci 0000:02:00.0: failed to wake target for read32 at 0x0003a028: -110
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: failed to read device register, device is gone
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: firmware crashed! (guid ff612ca1-711b-4011-8ec2-9a4e23859951)
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: qca6174 hw3.2 target 0x05030000 chip_id 0x00340aff sub 1a56:1535
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 0 testmode 0
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: firmware ver WLAN.RM.4.4.1-00079-QCARMSWPZ-1 api 6 features wowlan,ignore-otp crc32 fd869beb
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: board_file api 2 bmi_id N/A crc32 20d869c3
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: htt-ver 3.47 wmi-op 4 htt-op 3 cal otp max-sta 32 raw 0 hwcrypto 1
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: failed to read firmware dump area: -28
Sep 21 21:32:10 toronto kernel: ath10k_pci 0000:02:00.0: Copy Engine register dump:
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [00]: 0x00034400 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [01]: 0x00034800 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [02]: 0x00034c00 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [03]: 0x00035000 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [04]: 0x00035400 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [05]: 0x00035800 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [06]: 0x00035c00 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: [07]: 0x00036000 4294967295 4294967295 4294967295 4294967295
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: failed to reset chip: -5
Sep 21 21:32:11 toronto kernel: ath10k_pci 0000:02:00.0: Could not init hif: -5