ALSA: hda/realtek - Simplify alc885_fixup_macpro_gpio()

The fixup for Macbook Pro is nothing but setting the GPIO bits as
usual but with one exception: it adds some delay at writing the GPIO
bits.

Add a flag to put the conditional delay in the common helper, and
clean up alc885_fixup_macpro_gpio() with the new flag.

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