media: i2c: adv7842: remove open coded version of SMBus block write

The version here is identical to the one in the I2C core, so use the
latter version directly.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>