ARM: dts: imx: Add devicetree for Kobo Aura 2

This adds a devicetree for the Kobo Aura 2 Ebook reader. It is based
on boards marked with "37NB-E60QL0+4B1". It is equipped with an i.MX6SL
SoC.

Expected to work:
  - Buttons
  - Wifi (with external module)
  - LED
  - uSD
  - USB
  - RTC
  - Fuel Gauge
  - Backlight (if the required regulator is probed before the backlight,
    specifying a supply is not supported by backlightdriver)
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/Makefile

@@ -681,6 +681,7 @@ dtb-$(CONFIG_SOC_IMX6Q) += \
 	imx6s-dhcom-drc02.dtb
 dtb-$(CONFIG_SOC_IMX6SL) += \
 	imx6sl-evk.dtb \
+	imx6sl-kobo-aura2.dtb \
 	imx6sl-tolino-shine2hd.dtb \
 	imx6sl-tolino-shine3.dtb \
 	imx6sl-tolino-vision5.dtb \