ALSA: emu10k1 - Add dB range to Bass and Treble for SB Live!

As the "Wave", "Wave Surround" or "Front" Playback Volume must be
changed to 70% (i.e. -12 dB) so that distortion won't occur when
increase Bass and Treble from 50% to 100%, so the maximum gain in
Bass and Treble are +12 dB.

Signed-off-by: Raymond Yau <superquad.vortex2@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>