ARM: dts: meson8b: Add support for the Endless Mini (EC-100)

The Endless Mini (EC-100) is a grapefruit-sized computer based on the
Amlogic Meson8b (S805) SoC which comes in two variants.

Both variants have in common:
- Amlogic Meson8b (S805) SoC
- two USB 2.0 ports on the rear, one one the front (connected to the SoC
  through an internal hub)
- 3.5mm Stereo out and MIC combo port
- HDMI and CVBS output
- 5V power supply (rated at 3A / 15W)
- an internal embedded micro-controller (called "EC") which implements a
  "breathing" effect for the LED and allows shutting down (powering off)
  the whole device
- 10/100 Mbit/s Ethernet using an IC Plus IP101A/G PHY (note: the website
  incorrectly lists a Gigabit Ethernet port)
- the CPU voltage is regulated using a PWM regulator. The GPL sources of
  the EC-100 are using a PWM value of 0x1c0000 for 0.86V and a PWM value
  of 0x00001c for 1.14V. When using the XTAL (24MHz) as input this
  translates into a PWM period of 1148ns with 0.86V using a duty cycle of
  100% and 1.14V using a duty cycle of 0%.

The main differences are:
- the main indicator for the variant is the RAM size: the "cheaper"
  variant has 1 GB of RAM, while the more expensive one comes with 2GB
- the storage size differs: 24 GB vs 32 GB
- the "1 GB RAM" variant has Ethernet connectivity only, while the "2 GB"
  variant has a Realtek RTL8723BS SDIO chip which adds 802.11b/g/n wifi
  and Bluetooth 4.0 support

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>