Fix ws2811 timing

Hi,

This pull requests fixes intermittent flashing of LEDs and adds GDB support.

I verified the problem on my oscilloscope and the first pulse wasn't always the correct length when the timer is disabled after the DMA transfer.  If the timer is left enabled the problem goes away.

I'd like to see a solution where the timer can be disabled, i tried resetting various flags and counters etc but to no avail.