ARM: dts: Add am335x-pocketbeagle

PocketBeagle is an ultra-tiny-yet-complete open-source USB-key-fob computer.

This board family can be indentified by the A335PBGL in the at24 eeprom:
A2: [aa 55 33 ee 41 33 33 35  50 42 47 4c 30 30 41 32 |.U3.A335PBGL00A2|]

http://beagleboard.org/pocket
https://github.com/beagleboard/pocketbeagle



Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
CC: Tony Lindgren <tony@atomide.com>
CC: Jason Kridner <jkridner@beagleboard.org>
CC: Drew Fustini <drew@beagleboard.org>
CC: Peter Robinson <pbrobinson@redhat.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>