vidc: Migrate to ion_map_iommu() API.

Migrate video driver to use the ion_map_iommu() api,
this api provides the physical address if IOMMU is
not enabled.
If IOMMU is enabled in the system it provides the
virtual contigious address.

Change-Id: I8b2871538c05986811fb565f9ebf1344e848cc10
Signed-off-by: Deepak Kotur <dkotur@codeaurora.org>