ALSA: rme96: Add PM support v3

Without proper power management handling, the first use
of a Digi96/8 anytime after a suspend / resume cycle will
start playback with distortions.

v3: Abort if vmalloc() of suspend buffers fail, but do not
leak memory in that case.

[fixed wrong memory leak fix again -- tiwai]

Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>