msm: adsprpc: validate VMID before hyp assign

Verify that VMID is not NULL before hyp assign call in init process
and memory map on remote subsystem.

Change-Id: I10a96b4efde61c5aa572748dda3596fb2301c6b2
Acked-by: Thyagarajan Venkatanarayanan <venkatan@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>