staging: dwc2: remove use of bus_to_virt()

Remove the use of bus_to_virt() and just fail the transfer if an
unaligned buffer with no virtual address is found. AFAIK that
can't happen anyway.

Also change setting of coherent DMA mask to the normal 32 bits.
31 bits was only needed when calling bus_to_virt() AFAICR.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>