ARM: dts: keystone: add support for k2 Edison SoC and EVM

Keystone2 Edison (K2E) is a Quad Cortex A15 based SoC with
1 DSP. It has standard peripherals such as i2c, spi, uart, timer,
pcie, etc similar to k2hk, but without wireless hardwares. This
patch add support for k2 Edison SoC and EVM. This re-uses the common
keystone.dtsi to include common bindings across the various k2
devices.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>