[M] Change in coreboot[main]: src: Add and use POST_BOOTBLOCK_C_ENTRY

[Marshall Dawson (Code Review)]

Attention is currently required from: Arthur Heymans, Christian Walter, Felix Held, Fred Reitberger, Jason Glenesk, Jeff Daly, Johnny Lin, Jonathan Zhang, Lean Sheng Tan, Martin L Roth, Matt DeVillier, Raul Rangel, Subrata Banik, Tarun Tuli, Tim Chu, Vanessa Eusebio.

Marshall Dawson has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/71593?usp=email )

Change subject: src: Add and use POST_BOOTBLOCK_C_ENTRY
......................................................................

Patch Set 2:

(1 comment)

Patchset:

PS2: 
Maybe add src/soc/amd/common/block/cpu/noncar/bootblock.c and src/soc/amd/stoneyridge/bootblock.c for good measure