ARM: dts: imx: add devicetree for Tolino Shine 2 HD

This adds a devicetree for the Tolino Shine 2 HD Ebook reader. It is based
on boards marked with "37NB-E60QF0+4A2". It is equipped with an i.MX6SL
SoC.

Expected to work:
- Buttons
- Wifi
- Touchscreen
- LED
- uSD
- USB
- RTC

Not working due to missing drivers:
- Backlight (requires NTXEC driver)
- EPD

Not working due to unknown reasons:
- deep sleep (echo standby >/sys/power/state works),
  wakeup fails when imx_gpc_pre_suspend(true) was called.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>