ALSA: hda - Merge Realtek parser code to generic parser

Finally the whole generic parser code in Realtek driver is moved into
hda_generic.c so that it can be used for generic codec driver.
The old dumb generic driver is replaced.  Yay.

The future plan is to adapt this generic parser for other codecs,
i.e. the codec driver calls the exported functions in generic driver
but adds some codec-specific fixes and setups.

As of this commit, the complete driver code is still duplicated in
Realtek codec driver.  The big code reduction will come from now on.

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