intel: Rename config FSP_USES_MP_SERVICES_PPI to MP_SERVICES_PPI

This change renames config FSP_USES_MP_SERVICES_PPI to MP_SERVICES_PPI
in preparation to allow V1 and V2 versions of MP services PPI.

TEST=Verified that timeless build for brya, volteer, icelake_rvp,
elkhartlake_crb and waddledee shows no change in generated coreboot.rom

Change-Id: I04acf1bc3a3739b31d6e9d01b6aa97542378754f
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50275
Reviewed-by: Aamir Bohra <aamir.bohra@intel.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/cpu.c

@@ -334,7 +334,7 @@ void arch_bootstate_coreboot_exit(void)
  * function will always getting called from coreboot context
  * (ESP stack pointer will always refer to coreboot).
  *
- * But with FSP_USES_MP_SERVICES_PPI implementation in coreboot this
+ * But with MP_SERVICES_PPI implementation in coreboot this
  * assumption might not be true, where FSP context (stack pointer refers
  * to FSP) will request to get cpu_index().
  *