msm: cpp: Return appropriate error on checking physical address

Negative value is returned from msm_cpp_queue_buffer_info. The return
value expects physical address. This results in invalid value to be
returned as physical address during error scenarios causing iommu
page fault. Return zero value for address on any errors.

CRs-Fixed: 928920
Change-Id: Idbf634db3e737e55b07ab8b2805dc7de1d534c26
Signed-off-by: Krishnankutty Kolathappilly <kkolatha@codeaurora.org>