Change in coreboot[master]: soc/intel/fast_spi: Use `need_restore_mtrr()` to clear temp MTRR

[Arthur Heymans (Code Review)]

Attention is currently required from: Subrata Banik, Tim Wawrzynczak, Nick Vaccaro, Eric Lai, Werner Zeh.
Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63492 )

Change subject: soc/intel/fast_spi: Use `need_restore_mtrr()` to clear temp MTRR
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Patch Set 2:

(1 comment)

File src/cpu/x86/mtrr/mtrrlib.c:

https://review.coreboot.org/c/coreboot/+/63492/comment/24c2f280_f078272e 
PS1, Line 52: /* Need to restore mtrr later using remove_temp_solution. */
            : 	if (ENV_RAMSTAGE)
            : 		need_restore_mtrr();
> > Is this still an open? Or can this be merged?
>
> Yes, may be waiting for Arthur to share a feedback.

I provided some feedback on the wait for idle AP implementation.