perf tools: Use __BYTE_ORDER__

Switch from the libc-defined __BYTE_ORDER to the compiler-defined
__BYTE_ORDER__ in order to make endianness detection more robust, like
it was done for libbpf.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20211104132311.984703-1-iii@linux.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>