ALSA: hda - Fix undefined symbol due to builtin/module mixup

Even after the fix for leftover kconfig handling (commit f8f1becf),
the current code still doesn't handle properly the builtin/module
mixup case between the core snd-hda-codec and other codec drivers.
For example, when CONFIG_SND_HDA_INTEL=y and
CONFIG_SND_HDA_CODEC_HDMI=m, it'll end up with an unresolved symbol
snd_hda_parse_hdmi_codec.  This patch fixes the issue.

Now codec->parser points to the parser object *only* when a module
(either generic or HDMI parser) is loaded and bound.  When a builtin
symbol is used, codec->parser still points to NULL.  This is the
difference from the previous versions.

Fixes: f8f1becf

 ('ALSA: hda - Fix leftover ifdef checks after modularization')
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>