ALSA: rme: Avoid non-standard macro usage

Pass the device pointer from the PCI pointer directly, instead of a
non-standard macro.  The macro didn't give any better readability.

Along with it, drop the unnecessary assignment before the
snd_dma_alloc_pages() call and simplify by returning the error code
directly.

Link: https://lore.kernel.org/r/20191105151856.10785-23-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>