arm64: Use custom mmap function for noncoherent dma ops

The non-coherent dma ops remap memory with appropriate attributes.
This remapped address cannot be used with virt_to_page which
dma_common_mmap uses. Implement a custom (but very similar) function
which correctly calculates the physical address and remaps to userspace.

Change-Id: I3a85670d38b9c098af27a366c8421a616d6c815d
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>