gprofng: Use __x86_64__ instead of __x86_64

gprofng: Use __x86_64__ instead of __x86_64

With some compilers, only __x86_64__ is defined so use that
instead of __x86_64.

gprofng/ChangeLog
2025-05-30  Andrew Pinski  <quic_apinski@quicinc.com>
	* common/core_pcbe.c: s/__x86_64/__x86_64__/.
	* common/cpu_frequency.h: Likewise.
	* common/cpuid.c: Likewise.
	* common/gp-defs.h: Likewise.
	* common/hwctable.c: Likewise.
	* libcollector/libcol-i386-dis.c: Likewise.
	* libcollector/libcol_util.h: Likewise.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>