ALSA: hda/realtek - Rename add_new_out_path() with add_new_nid_path()

Make the function more generic for both input and output directions,
and returns the assigned path pointer.  The argument order is changed
to follow the standard (from, to) way.

Now this new function is used for analog input and loopback path
parser codes, too.

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