[M] Change in coreboot[main]: vc/google/chromeos: Implement dynamic ChromeOS boot logo selection

[Gwendal Grignou (Code Review)]

Attention is currently required from: Kapil Porwal, Paul Menzel, Paz Zcharya, Subrata Banik.

Gwendal Grignou has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/80738?usp=email )

Change subject: vc/google/chromeos: Implement dynamic ChromeOS boot logo selection
......................................................................

Patch Set 9: Code-Review-1

(2 comments)

File src/vendorcode/google/chromeos/tpm_factory_config.c:

https://review.coreboot.org/c/coreboot/+/80738/comment/8b13d103_39dce3e4 :
PS9, Line 61: 	return (factory_config & CHROMEBOOK_PLUS_DEVICE) == CHROMEBOOK_PLUS_DEVICE;
That won't work for future device, since feature_level could be 2. Beside, hard branded device is enough to display the hard branded logo, so
```
return (factory_config & CHROMEBOOK_PLUS_HARD_BRANDED) == CHROMEBOOK_PLUS_HARD_BRANDED;
```
is enough.

https://review.coreboot.org/c/coreboot/+/80738/comment/6546a377_3db07331 :
PS9, Line 80: 	 */
Let document further to explain the `CAE` magic since we are not going to put protobuf library in the near future:
```
/*
 * |feature_device_info| contains a base64-encoded protobuf and the first entry is 
 * |feature_level|, greater than 1 for chromebook X device.
 * (see https://chromium.googlesource.com/chromiumos/platform/feature-management/+/r...)
 *
 * The first byte currently hold the feature level.
 /
 const char decoded_feature_device_info[B64_DECODED_SIZE(VPD_FEATURE_DEVICE_INFO_LEN)];

if (b64_decode(feature_device_info, strlen(feature_device_info), decoded_feature_device_info)) > 0)
   return decoded_feature_device_info[0] > 1;
 else
   return false;
 ```