Patch from Nicolas Pitre

Since we know the value of cpsr on entry, we can replace the bic+orr with
a single eor.  Also remove a possible result delay (at least on XScale).
Signed-off-by: NNicolas Pitre <nico@cam.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>