ARM: dts: NSP: Add common bindings for MX64/MX65

These bindings are required for all Meraki MX64/MX65 devices. These
common bindings include memory (2GB), PWM LEDs, AMAC, I2C (AT24), NAND
partitions, EHCI, OHCI and pinctrl.

Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>