Change in coreboot[master]: cpu/intel/car/p4: Add x86_64 support

[Nico Huber (Code Review)]

Attention is currently required from: Arthur Heymans, Patrick Rudolph.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56021 )

Change subject: cpu/intel/car/p4: Add x86_64 support
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Patch Set 4: Code-Review+2

(2 comments)

File src/cpu/intel/car/p4-netburst/cache_as_ram.S:

https://review.coreboot.org/c/coreboot/+/56021/comment/8372a14e_a9afeffe 
PS4, Line 364: 	#include <cpu/x86/64bit/entry64.inc>
Oddly named, I had to think twice to understand what to expect
in there. It's more `enter64`. `entry16.inc` and `entry32.inc`
both define the entry point after switching the mode.

https://review.coreboot.org/c/coreboot/+/56021/comment/bbcb0d70_2e263b8f 
PS4, Line 365: 
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