media: v4l2-ctls-core.c: kvmalloc_array -> kvcalloc

Fixes smatch warning:

drivers/media/v4l2-core/v4l2-ctrls-core.c:1143 v4l2_ctrl_handler_init_class() warn: Please consider using kvcalloc instead

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>