signal/x86: Remove pkey parameter from mm_fault_error

After the previous cleanups to do_sigbus and and bad_area_nosemaphore
mm_fault_error no now longer uses it's pkey parameter.  Therefore
remove the unused parameter.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>