Fix hp_pin always no value.

[More notes on the changes:

 The hp_pin value that is referred in alc294_hp_init() is always zero
 at the moment the function gets called, hence this is actually
 useless as in the current code.

 And, this kind of init sequence should be called from the codec init
 callback, instead of the parser function.  So, the first fix in this
 patch to move the call call into its own init_hook.

 OTOH, this function is needed to be called only once after the boot,
 and it'd take too long for invoking at each resume (where the init
 callback gets called).  So we add a new flag and invoke this only
 once as an additional fix.

 The one case is still not covered, though: S4 resume.  But this
 change itself won't lead to any regression in that regard, so we
 leave S4 issue as is for now and fix it later.  -- tiwai ]

Fixes: bde1a745 ("ALSA: hda/realtek - Fixed headphone issue for ALC700")
Signed-off-by: Kailang Yang <kailang@realtek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>