msm: smp2p: Use uintptr_t for conversions between ints and pointers

Conversions between integers and pointers should use the uintptr_t type.

Use the uintptr_t type in conversions between pointers and integers where
necessary.

Change-Id: Ic9a93f72c07b8a6c809d011b0c98a55ee683ce33
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>