/dev/mem: use phys_addr_t for physical addresses

This patch fixes the /dev/mem driver to use phys_addr_t for physical
addresses.  This is required on PAE systems, especially those that run
entirely out of >4G physical memory space.

Signed-off-by: Cyril Chemparathy <cyril@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>