msm: vidc: Copy the reserved fields back to userpace

The reserved fields, which contain fd and offset, should be copied
back to userspace. This saves book keeping (which index matches to
which fd/offset) on userspace client.

Change-Id: I1f3333c874099f33eb0b1fa73c8cb3265eea6ee3
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>