Change in coreboot[master]: cpu/x86/mtrrlib: Use `need restore mtrr()` from set var mtrr function

[Werner Zeh (Code Review)]

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

Change subject: cpu/x86/mtrrlib: Use `need_restore_mtrr()` from  set_var_mtrr  function
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Patch Set 1:

(1 comment)

Patchset:

PS1: 
Prior to this patch I did have errors in dmesg related to MTRR setup in Linux:

mtrr: your CPUs had inconsistent variable MTRR settings                               
mtrr: probably your BIOS does not setup all CPUs.
mtrr: corrected configuration.

With this patch everything looks good again and the flash caching works as needed.