Added LED driver using status_led. USR0 is set to monitor the boot
status. USR1 is set to be the GREEN LED.
To simplify booting into various boot configurations, there is now a
test for an existing ramdisk.gz image if loading the boot script fails.
Adding additional boot arguments can also be done using optargs.
Signed-off-by: Jason Kridner <jkridner@beagleboard.org>