Change in coreboot[master]: arch/x86: Add a common romstage entry

[Angel Pons (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Furquan Shaikh, Marshall Dawson, Arthur Heymans, Patrick Rudolph, Felix Held.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/55067 )

Change subject: arch/x86: Add a common romstage entry
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Patch Set 2:

(2 comments)

File src/arch/x86/romstage.c:

https://review.coreboot.org/c/coreboot/+/55067/comment/fee63585_eadfa494 
PS2, Line 7: static void _romstage_main(void)
Does this need to be a separate function?

File src/include/romstage_common.h:

https://review.coreboot.org/c/coreboot/+/55067/comment/11ea18c8_a99cfaa8 
PS2, Line 3: __ROMSTAGE_COMMON_H
Identifiers starting with two leading underscores are reserved. I'd just name this `ROMSTAGE_COMMON_H`