soc: qcom: access smp2p_smem structure with I/O function

Accessing I/O memory pointers directly cause un-aligned access
when using the clang compiler.

Avoid using direct iomem pointer access instead use I/O functions.

CRs-Fixed: 2410460
Change-Id: I041b10739049de26174e5536bbd142f1deeada3b
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>