[ALSA] ak4xxx - Remove bogus IPGA controls

Remove IPGA volume controls and merge the IPGA range to ADC volume
controls.  These two volumes are not really independent but connected
simply in different ranges 0-0x7f and 0x80-max.  It doesn't make sense
to provide two controls.
Since both 0x7f and 0x80 specify 0dB, a hack is needed for IPGA range
to skip 0x80 (increment one) for such controls.

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