media: tvp5150: make use of regmap_update_bits

Since commit 9a4c7e68f7e0 ("media: tvp5150: convert register
access to regmap")' the driver supports regmap. Now we can drop
the handmade bit update sequence and move to the regmap provided
helpers.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>