beaglebone: Add code to set the value of the LEDs

The LEDs on the beaglebone are connected to GPIOs called USR0-USR3. This
change adds some functions to make it easy to set their value and clear
what the calling code is trying to do.

Change-Id: I0bb83bbc2e195ce1a0104afcd120089efaa22916
Signed-off-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: https://review.coreboot.org/3943
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
3 files changed