Change in flashrom[master]: sb600spi.c: Use SPI100 bit mappings

[Felix Held (Code Review)]

Attention is currently required from: Robert Zieba, Paul Menzel, Jon Murphy, Edward O'Callaghan, Karthik Ramasubramanian.
Felix Held has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/63422 )

Change subject: sb600spi.c: Use SPI100 bit mappings
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Patch Set 2:

(2 comments)

Commit Message:

https://review.coreboot.org/c/flashrom/+/63422/comment/f066a9cd_aef12d9c 
PS1, Line 8: 
           : Flashrom has been using legacy spi100 bit mappings when programming the
           : opcode and triggering the command. These legacy bit mappings are
           : deprecated in upcoming generation of AMD SoCs.
> Added more details relevant to this CL. […]

spi_ctrlr_xfer in soc/amd/common/block/spi/fch_spi_ctrl.c in coreboot might clarify a bit how this spi100 engine is used

https://review.coreboot.org/c/flashrom/+/63422/comment/3bf8fcf4_796507e9 
PS1, Line 11: Stop using the legacy
            : spi100 registers and use the correct ones.
> Done

give me a few hours to check with the docs that this won't break things on older platforms before landing this patch