Stellaris: Do not use blocking delays when flashing the green LED

The main loop is useful for more than just flashing an LED. Don't use
blocking delays for controlling the LED.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Stellaris: Use correct nibble order in LPC write cycle

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>