ARM: dts: Add support for dra76x family of devices

dra76 family is a high-performance, infotainment application
device, based on OMAP architecture on a 28-nm technology.
This contains most of the subsystems, peripherals that are
available on dra74, dra72 family. This SoC mainly features
Subsystems:
- 2 x Cortex-A15 with max speed of 1.8GHz
- 2 X DSP
- 2 X Cortex-M4 IPU
- ISS
- CAL
- DSS
- VPE
- VIP
Connectivity peripherals:
- 1 USB3.0 and 3 USB2.0 subsystems
- 2 x SATA
- 2 x PCI Express Gen2
- 3-port Gigabit ethernet switch
- 2 x CAN
- MCAN

Adding basic dts support for DRA76 family while reusing the
data available in dra7.dtsi, dra74x.dtsi.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>