coresight: etb10: Move etb_disable_hw() outside of lock

Function etb_disable_hw() is already taking care of unlocking and locking
the coresight access register and as such doesn't need to be placed
within the unlock/lock of function etb_update_buffer().

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>