msm: vidc: Separate partition for shared memory

Create separate partition for shared command
queues. Virtual device addresses for shared
command queues need to be from upper 16MB
region of mon-secure virtual device address
space. This change creates a partition to
ensure this.

Change-Id: Iba22daf93b7d08c70f43685de7182a2f235a7690
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>