[PATCH] ARM: Move copy/clear user_page locking into implementation

Move the locking for copy_user_page() and clear_user_page() into
the implementations which require locking.  For simple memcpy/
memset based implementations, the locking is extra overhead which
is not necessary, and prevents preemption occuring.

Signed-off-by: Russell King <rmk@arm.linux.org.uk>