uc20 armhf image does not boot on rpi4-8GB

[Paul Larson]

The image can be found here: http://cdimage.ubuntu.com/ubuntu-core/20/dangerous-beta/20201202.1/ubuntu-core-20-armhf+raspi.img.xz

This image seems to be booting fine on other RPI devices, including other RPI4 devices with 4/2/1GB
Also, the arm64 image boots fine on this device. It's just the combination of armhf image on rpi4b-8GB that seems to fail.

Here's all I got from serial when it tries to boot:

U-Boot 2020.10+dfsg-1ubuntu0~20.04.1 (Nov 12 2020 - 17:05:18 +0000)

DRAM: B
MMC: mmcnr@7e300000: 1, emmc2@7e340000: 0
Loading Environment from FAT... In: serial
Out: serial
Err: serial
Net: eth0: ethernet@7d580000
PCIe BRCM: link up, 5.0 Gbps x1 (SSC)
starting USB...
Bus xhci_pci: probe failed, error -110
No working controllers found