driver: video: enable msm vidc independently of FB_MSM

Historically, the VIDC driver has been put in driver/video/msm and requires
FB_MSM to enabled so that it can be built. Now that we have DRM_MSM we want to
be able to use VIDC without FB_MSM...

We could move vidc out of drivers/video/msm, however that would make
merge/cherry-pick problematic. So for now, let's just allow to select VIDC
without FB_MSM.

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>