ALSA: hda/realtek - Support Dell headset mode for ALC288

Dell create new platform with ALC288 codec.
This patch will enable headset mode for Dino platform.

[slight code refactoring and compile fix by tiwai]

Signed-off-by: Kailang Yang <kailang@realtek.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>