x86, cpufeature: Remove stray %s, add -w to mkcapflags.pl

There was a stray %s left from testing, remove it.

Add -w to the #! line (which is parsed by Perl even if the Perl
interpreter is invoked explicitly on the command line) to catch these
kinds of errors in the future.

Reported-by: Jean Delvare <khali@linux-fr.org>
Link: http://lkml.kernel.org/r/20120626143246.0c9bf301@endymion.delvare
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>