[ALSA] hdsp - Fix auto-updating of firmware

Fixed the auto-updating of firmware if the breakout box was switched
off/on.  The firmware binary itself was already cached but it wasn't
loaded properly.  Also, request_firmware() is issued if the box was
with firmware at module loading time but later it's erased.
The auto-update is triggered at each PCM action (open, prepare, etc)
and at opening proc files.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>