ALSA: hda - Don't release firmware when CONFIG_PM is set

The new firmware code tries to re-read the formerly read firmware
files before suspend.  Thus it's wiser to keep the "patch" firmware in
the driver for avoiding this unnecessary re-reading.

Of course, this will consume a bit of memory for unused stuff, but
the patch fw is supposed to be fairly small, so it's more benefit in
the end.

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