EV3 PRU

Changelog:

• Add PWM for LEDs

Ships as part of ev3dev kernel:

ev3dev/lego-linux-drivers@254de3d#diff-6c203bd0487c3122c18e9a585bd0005f

PRU with tachometer for FatcatLab EVB

evb-pru0: implement tachometer

copied from ev3-pru1 and modified for BeagleBone

EV3 PRU firmware with tachometer

ev3-pru1-v1.0.0

ev3-pru1: update ring buffer size to match evb-pru0

Test firmware for tacho counter on LEGO MINDSTORMS EV3

This shipped in the firmware-ev3 3 package https://github.com/ev3dev/firmware-ev3/releases/tag/ev3dev-stretch%2F3

Firmware for testing mainline kernel remoteproc driver

Snapshot of firmware for testing mainline kernel remoteproc driver.