[ALSA] hdsp - Add support for fine tuning of sample rate support to HDSP 9632

Add 'DDS Sample Rate Offset' control. Allows values in Hz from -5000 to +5000.
The value is added to the nominal sample rate and written to the DDS register.

Signed-off-by: Julian Cable <julian_cable@yahoo.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>