msm: adsprpc: use same CPU address during DMA allocation and free

Ensure that the same CPU address returned from the DMA memory
allocation API is passed to the DMA memory free API.

Change-Id: I09d23fb9960bc3400f85aef84bb16d64b546b112
Acked-by: Thyagarajan Venkatanarayanan <venkatan@qti.qualcomm.com>
Signed-off-by: Mohammed Nayeem Ur Rahman <mohara@codeaurora.org>