msm: adsprpc: use right DMA bit mask for 32 and 64 bit systems

Use right length of DMA bit mask for 32 and 64 bit systems by
typecasting it to the appropriate data type

Change-Id: Ie7346fe950408e510a6b529b25f0dc57eb3ee438
Acked-by: Thyagarajan Venkatanarayanan <venkatan@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>