CRIS: fix defconfig build failure

The CRIS defconfig fails to build with:

  drivers/serial/crisv10.c: In function 'rs_wait_until_sent':
  drivers/serial/crisv10.c:3926: error: implicit declaration of function 'lock_kernel'
  drivers/serial/crisv10.c:3943: error: implicit declaration of function 'unlock_kernel'

Include smp_lock.h.

LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>