ARM: dma: use phys_addr_t in __dma_page_[cpu_to_dev/dev_to_cpu]

On a 32 bit ARM architecture with LPAE extension physical addresses
cannot fit into unsigned long variable.

So fix it by using phys_addr_t instead of unsigned long.

Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>