[media] ARM: PXA: use gpio_set_value_cansleep() on pcm990

Camera-switching GPIOs are provided by a i2c GPIO extender, switching
them can send the caller to sleep. Use the GPIO API *_cansleep methods
explicitly to avoid runtime warnings.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>