Change in coreboot[master]: soc/amd: Throw an error if FWM_POSITION_INDEX is empty

[Bao Zheng (Code Review)]

Attention is currently required from: Jason Glenesk, Martin Roth, Marshall Dawson, Zheng Bao, Felix Held.
Bao Zheng has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/49855 )

Change subject: soc/amd: Throw an error if FWM_POSITION_INDEX is empty
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Patch Set 7:

(2 comments)

File src/soc/amd/cezanne/Makefile.inc:

https://review.coreboot.org/c/coreboot/+/49855/comment/8ffa6090_64e078b6 
PS5, Line 44: $(if $(CONFIG_AMD_FWM_POSITION_INDEX), ,
> Maybe something like  "Invalid AMD firmware position index - Check if the board sets a valid ROM siz […]

Done

File src/soc/amd/cezanne/Makefile.inc:

https://review.coreboot.org/c/coreboot/+/49855/comment/e3828061_07caed19 
PS6, Line 48: CONFIG_BOARD_ROMSIZE_KB_16384
> Any reason not to add COREBOOT_ROMSIZE_KB_32768 & COREBOOT_ROMSIZE_KB_65536? They should both be sup […]

Done.
Not involved with ROM_SIZE now.