msm: vidc: Fix IOMMU pagefault for long clips

Shared command/message queues are circular, so if they get
full driver has to write/read into them from the beginning.
The address used to write/read from beginning was not the
kernel virtual address causing IOMMU page fault.

CRs-fixed: 400747
Change-Id: Ie414f75370c31c8a4fb1bf7c879d1d0f4d5c7ea0
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>