USB Type-C Alternate Mode support

[quanxian]

Description
Let's track here the progress for generic alternate mode support. The discovery and entering/exiting the modes is common for all alternate modes, and the USB PD code will handle that. The tasks currently related to this task are:

1) The alternate modes will need custom control that we don't want to mix into the generic USB PD code. For example the DP altmode defines custom VDM (Vendor Defined Message) for "configure" and "status" commands. So we will need to create somekind of API for Alternate Mode "drivers".

2) The Alternate Modes need to keep the underlying components and drivers informed about their status, possibly even allow some control. For example, with DP altmode the graphics side will need to know the cable orientation and the number of lanes (the modes define the pin configuration in DP altmode, so the numer of available lanes as well AFAIK). So we need API for this.

*) UCSI may need some special attention, as with UCSI we don't handle the USB PD communication. We just get the status of the port. But we will know which alternate mode has been enterred, and we can actually request enter/exit a mode even with UCSI. But we don't know for example the cable orientation.

Commits:
0e3bb7d6894d9b6e67d6382bb03a46a1dc989588 49cbb33dfdeb7651b91c2316a61b644d8e6cfe22 4ab8c18d4d67321cc7b660559de17511d4fc0237 8a37d87d72f0c69f837229c04d2fcd7117ea57e7 93dd2112c7b2fa5512cc4aff2c449420487fcb68 e9576fe8e605c4413beb91b290b8a473985710de

Target Kernel: 4.19
Target Release: 19.04