Change in coreboot[master]: src/lib: Support fallback option for fw_config

[Subrata Banik (Code Review)]

Attention is currently required from: Furquan Shaikh, Jamie Ryu, Wonkyu Kim, Ravishankar Sarawadi, Tim Wawrzynczak, Julius Werner, Nick Vaccaro, Raj Astekar, Srinidhi N Kaushik.
Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/58833 )

Change subject: src/lib: Support fallback option for fw_config
......................................................................

Patch Set 4:

(2 comments)

File src/Kconfig:

https://review.coreboot.org/c/coreboot/+/58833/comment/a6bed50d_9dbdd6c2 
PS4, Line 408: FW_CONFIG_SOURCE_CBFS
why can't FW_CONFIG_SOURCE_CBFS Kconfig exist in line 398 above ?

https://review.coreboot.org/c/coreboot/+/58833/comment/6f77b591_67b927b8 
PS4, Line 416: and 
remove one "and"?

why not append this at line 406 itself ?