ALSA: hda - Use IS_REACHABLE() for dependency on input

The commit ffcd28d8 ("ALSA: hda - Select INPUT for Realtek
HD-audio codec") introduced the reverse-selection of CONFIG_INPUT for
Realtek codec in order to avoid the mess with dependency between
built-in and modules.  Later on, we obtained IS_REACHABLE() macro
exactly for this kind of problems, and now we can remove th INPUT
selection in Kconfig and put IS_REACHABLE(INPUT) to the appropriate
places in the code, so that the driver doesn't need to select other
subsystem forcibly.

Fixes: ffcd28d8 ("ALSA: hda - Select INPUT for Realtek HD-audio codec")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # and build-tested
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/Kconfig

@@ -88,7 +88,6 @@ config SND_HDA_PATCH_LOADER
 config SND_HDA_CODEC_REALTEK
 	tristate "Build Realtek HD-audio codec support"
 	select SND_HDA_GENERIC
-	select INPUT
 	help
 	  Say Y or M here to include Realtek HD-audio codec support in
 	  snd-hda-intel driver, such as ALC880.

sound/pci/hda/patch_realtek.c

@@ -3810,6 +3810,7 @@ static void alc280_fixup_hp_gpio4(struct hda_codec *codec,
 	}
 }
 
+#if IS_REACHABLE(INPUT)
 static void gpio2_mic_hotkey_event(struct hda_codec *codec,
 				   struct hda_jack_callback *event)
 {
@@ -3942,6 +3943,10 @@ static void alc233_fixup_lenovo_line2_mic_hotkey(struct hda_codec *codec,
 		spec->kb_dev = NULL;
 	}
 }
+#else /* INPUT */
+#define alc280_fixup_hp_gpio2_mic_hotkey	NULL
+#define alc233_fixup_lenovo_line2_mic_hotkey	NULL
+#endif /* INPUT */
 
 static void alc269_fixup_hp_line1_mic1_led(struct hda_codec *codec,
 				const struct hda_fixup *fix, int action)