msm: Update the permissions while making assign call

When memory that is assigned a particular VMID is re-assigned
back to HLOS, it needs to get RWX permissions so that HLOS can
use it for data as well as instructions.

Change-Id: Ib5413861de877d9081bdf5bd397f528293deb6e8
Signed-off-by: Neeti Desai <neetid@codeaurora.org>