media: ov7740: use SCCB regmap

Make use of SCCB APIs for regmap operations.
Remove i2c_check_functionality as devm_regmap_init_sccb
does it for us.

Signed-off-by: Raag Jadav <raagjadav@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>