layer.conf: Remove references to i2s-mmap

This overlay is gone in Linux 4.9 which Pyro uses for all machine
types.

Signed-off-by: Will Newton <willn@resin.io>

layers/meta-resin-raspberrypi/conf/layer.conf

@@ -42,7 +42,6 @@ KERNEL_DEVICETREE_append = " \
     overlays/i2c-pwm-pca9685a.dtbo \
     overlays/i2c-sensor.dtbo \
     overlays/i2s-gpio28-31.dtbo \
-    overlays/i2s-mmap.dtbo \
     overlays/iqaudio-digi-wm8804-audio.dtbo \
     overlays/justboom-dac.dtbo \
     overlays/justboom-digi.dtbo \
@@ -96,10 +95,5 @@ KERNEL_DEVICETREE_append = " \
     overlays/wittypi.dtbo \
 "
 
-# XXX
-# Ugly hack - the 4.9 Kernel, on which RaspberryPi 3 64 is, doesn't provide
-# i2s-mmap anymore
-KERNEL_DEVICETREE_remove_raspberrypi3-64 = "overlays/i2s-mmap.dtbo"
-
 # We use udev rules to create serial device aliases
 SERIAL_CONSOLE = "115200 serial0"