Buzzer working. TA1CCR0 is set by the GPIO pin interrupt callback
function. Setting the TA1CCR0 register sets the frequency, which also,
in "UP" mode, turns on the timer and starts the tone. TA1CCR0 is set
back to zero by the TA0CCR1 interrupt callback function. Setting the
TA1CCR0 register to zero while the timer is configured in "UP"mode stops
the timer which stops the tone.