This patch applies the microphone-related fix created for the Acer
Aspire E1-572 to the E1-472 as well, as it uses the same Realtek ALC282
CODEC and demonstrates the same issues.

This patch allows an external, headset microphone to be used and limits
the gain on the (quite noisy) internal microphone.
Signed-off-by: Simon South <simon@simonsouth.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>