ALSA: hda - Clean up Cxt5047 parser

Clean up Conexant 5047 pareser code:
 - Split mixer elements to separate arrays to reduce the duplicated
   entires
 - Fix mixer element names to the standard ones
 - Remove unneeded cxt5047_hp2_unsol_event; the normal unsol_event
   handler works fine.

Signed-off-by: Takashi Iwai <tiwai@suse.de>