ARM: dts: imx: Add Y Soft IOTA Draco, Hydra and Ursa boards

These are i.MX6S/DL based SBCs embedded in various Y Soft products.
All share the same board design but have slightly different HW
configuration.

Ursa
- i.MX6S SoC, 512MB RAM DDR3, 4GB eMMC, microSD
- parallel WVGA 7" LCD with touch panel
- 1x Eth (QCA8334 switch)
- USB OTG
- USB host (micro-B)

Draco
- i.MX6S SoC, 512MB RAM DDR3, 4GB eMMC, microSD
- parallel WVGA 7" LCD with touch panel
- 2x Eth (QCA8334 switch)
- USB OTG
- USB host (micro-B)
- RGB LED (I2C LP5562)
- 3.5mm audio jack + codec (LM49350)

Hydra
- i.MX6DL SoC, 2GB RAM DDR3, 4GB eMMC, microSD
- I2C OLED display, capacitive matrix keys
- 2x Eth (QCA8334 switch)
- USB OTG
- RGB LED (I2C LP5562)
- 3.5mm audio jack + codec (LM49350)
- HDMI
- miniPCIe slot

Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>