cpu/x86/mtrr: add x86_setup_mtrrs_with_detect_no_above_4gb()

There's not a function that is the equivalent to
x86_setup_mtrrs_with_detect() but not solving for above 4GiB.
Provide x86_setup_mtrrs_with_detect_no_above_4gb() which is the
equivalent to x86_setup_mtrrs_with_detect() but instructs the MTRR
solver to not take into account memory above 4GiB.

BUG=b:155426691

Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Change-Id: Ia1b5d67d6f139aaa929e03ddbc394d57dfb949e0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41897
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/cpu/x86/mtrr.h

@@ -77,6 +77,7 @@ void x86_setup_mtrrs(void);
  * it always dynamically detects the number of variable MTRRs available.
  */
 void x86_setup_mtrrs_with_detect(void);
+void x86_setup_mtrrs_with_detect_no_above_4gb(void);
 /*
  * x86_setup_var_mtrrs() parameters:
  * address_bits - number of physical address bits supported by cpu