coresight: tpiu: Cleanup power management

Drop the power only when we have successfully probed. Otherwise
leave it to the amba probe to do the rest.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[Removed extra newline left after original modification]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>