media: drivers: media: platform: make VIDEO_VIU depend on I2C

Commit 7378f114 ("media: omap2: omapfb: allow building it with
COMPILE_TEST") broke compilation without CONFIG_I2C selected.
drivers/media/platform/fsl-viu.c: In function ‘viu_of_probe’:
drivers/media/platform/fsl-viu.c:1452:7: error: implicit declaration of function ‘i2c_get_adapter’; did you mean ‘i2c_lock_adapter’? [-Werror=implicit-function-declaration]
  ad = i2c_get_adapter(0);
       ^~~~~~~~~~~~~~~
       i2c_lock_adapter
drivers/media/platform/fsl-viu.c:1452:5: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
  ad = i2c_get_adapter(0);
     ^
drivers/media/platform/fsl-viu.c:1534:2: error: implicit declaration of function ‘i2c_put_adapter’; did you mean ‘i2c_lock_adapter’? [-Werror=implicit-function-declaration]
  i2c_put_adapter(ad);
  ^~~~~~~~~~~~~~~
  i2c_lock_adapter

Added I2C dependency in order to make all configurations work again.

Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>