x86, cpufeature: Unbreak compile with gcc 3.x

gcc 3 is too braindamaged to be able to compile static_cpu_has() --
apparently it can't tell that a constant passed to an inline function
is still a constant -- so if we're using gcc 3, just use the dynamic
test.  This is bad for performance, but if you care about performance,
don't use an ancient, known-to-optimize-poorly compiler.

Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
LKML-Reference: <4BF2FF82.7090005@zytor.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>