compiler.h: use the correct symbol to test for __builtin_expect()
compiler.h: use the correct symbol to test for __builtin_expect()

__builtin_expect() has leading underscores, they need to be reflected
in the symbol.

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@linux.intel.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm