Now that _exception no longer calls _exception_pkey it is no longer
necessary to handle any signal with any si_code.  All pkey exceptions
are SIGSEGV with paired with SEGV_PKUERR.  So just handle
that case and remove the now unnecessary parameters from _exception_pkey.
Reviewed-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>