adsprpc: Increment map size for each entry in SGL

Incrementally update the memory map size from each entry in the
DMA scatter-gather list.

Change-Id: Ia44d5140df3de385ca0324b540c8ad715f5f087b
Acked-by: Thyagarajan Venkatanarayanan <venkatan@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>