V4L/DVB (13286): pxa-camera: Fix missing sched.h

Required for wakeup call.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>