cpu/x86/lapic: Separate stop_this_cpu()

Function is needed with PARALLEL_MP and excluding guard will
be added to the source file.

The incompatibilities with X2APIC_SUPPORT have been fixed
so the exclusion is removed here too.

Change-Id: I5696da4dfe98579a3b37a027966b6758f22574aa
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55193
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/include/cpu/x86/lapic.h

@@ -159,7 +159,7 @@ static __always_inline unsigned int lapicid(void)
 
 #if !CONFIG(AP_IN_SIPI_WAIT)
 /* If we need to go back to sipi wait, we use the long non-inlined version of
- * this function in lapic_cpu_init.c
+ * this function in lapic_cpu_stop.c
  */
 static __always_inline void stop_this_cpu(void)
 {