google/snappy: update timing of sdmode toggling

Maxim98357a speaker amp requires BCLK & SFRM to be active
and stable before it is unmuted. If there is a BLCK and no
SFRM, it results in a pop sound.

sdmode_delay property already exists which facilitates this
configuration. This patch updates "sdmode_delay" to avoid
pop sound.

BUG=chrome-os-partner:59034
BRANCH=master
TEST=emerge-snappy coreboot chromeos-bootimage

Change-Id: Ic9095ae6812ba822c760229e69f5b27c6c244cdf
Signed-off-by: Wisley Chen <wisley.chen@quantatw.com>
Reviewed-on: https://review.coreboot.org/17361
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/mainboard/google/reef/variants/snappy/devicetree.cb

@@ -90,6 +90,7 @@ chip soc/intel/apollolake
 		device pci 0e.0 on	# - Audio
 			chip drivers/generic/max98357a
 				register "sdmode_gpio" =  "ACPI_GPIO_OUTPUT_ACTIVE_HIGH(GPIO_76)"
+				register "sdmode_delay" = "5"
 				device generic 0 on end
 			end
 		end