This patch STV090X adds and exports a function to control the GPIOs of
the stv090x-devices.

Cc: Manu Abraham <abraham.manu@gmail.com>
Signed-off-by: NMartin Wilks <m.wilks@technisat.com>
Signed-off-by: NPatrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>