media: tw9910: add helper function for setting gpiod value

tw9910 driver tries to sleep for the same period of time
after each gpiod_set_value(). The patch moves duplicated code
to a helper function.

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>