kuap_save_and_lock() is only for interrupts inside kernel.

system call are only from user, calling kuap_save_and_lock()
is wrong.

Fixes: c1672883 ("powerpc/32: Manage KUAP in C")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/332773775cf24a422105dee2d383fb8f04589045.1620302182.git.christophe.leroy@csgroup.eu