Fix the following sparse warnings:

ti-vpe/cal.c:387:26: warning: incorrect type in return expression (different address spaces)
ti-vpe/cal.c:459:26: warning: incorrect type in return expression (different address spaces)
ti-vpe/cal.c:503:27: warning: incorrect type in argument 6 (different address spaces)
ti-vpe/cal.c:509:47: warning: incorrect type in argument 6 (different address spaces)
ti-vpe/cal.c:518:47: warning: incorrect type in argument 6 (different address spaces)
ti-vpe/cal.c:526:31: warning: incorrect type in argument 6 (different address spaces)
ti-vpe/cal.c:1807:24: warning: Using plain integer as NULL pointer
ti-vpe/cal.c:1844:16: warning: Using plain integer as NULL pointer
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>