ALSA: hda - Fixed internal mic initialization for Dell Vostro 1015

Fixed initialization of internal mic and added internal mic boost control
Renamed analog mic boost control to ext mic boost contol.
Name pair analog/digital seems too confusing for a normal user.

Signed-off-by: Einar Rünkaru <einarry@smail.ee>
Signed-off-by: Takashi Iwai <tiwai@suse.de>