Change in coreboot[master]: soc/intel/broadwell: Drop `SPIBARx` macros

[Nico Huber (Code Review)]

Attention is currently required from: Angel Pons, Arthur Heymans, Patrick Rudolph.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50042 )

Change subject: soc/intel/broadwell: Drop `SPIBARx` macros
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Patch Set 2:

(1 comment)

Patchset:

PS2: 
The current situation is a mess, I known. But I'm not sure
if this doesn't make it worse. Intel has (almost?) always
documented the SPIBAR separately, even if its location was
implicitly configured relative to RCBA. Also, newer chipsets
have a separate BAR now (with mostly identical registers).

So it would seem much more future-proof to have SPIBAR macros
or functions.