media: ti-vpe: cal: Use a loop to create CAMERARX and context instances

Replace a manually unrolled loop with an explicit for loop to increase
readability when creating the CAMERARX and context instances. The
explicit NULL initialization of cal->phy[] and cal->ctx[] is removed, as
the cal structure is zeroed when allocated.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>