msm: memory: Use phys_addr_t for memory reservation code

When reserving memory, the reserved regions may be placed above
a 32-bit address on LPAE based systems. Adjust the reservation code to
account for this.

Change-Id: If7e1775352d2557106cca0b50caec3d5134e0174
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>