ARM: mm: use phys_addr_t appropriately in p2v and v2p conversions

Fix remainder types used when converting back and forth between
physical and virtual addresses.

Cc: Russell King <linux@arm.linux.org.uk>

Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>