media: ti-vpe: cal: Use syscon_regmap_lookup_by_phandle_args()

Use the syscon_regmap_lookup_by_phandle_args() function to replace
manual lookup of the syscon regmap offset. This simplifies the
cal_camerarx_init_regmap() implementation.

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>