reset: make shared pulsed reset controls re-triggerable

The current reset framework API does not allow to release what is done by
reset_control_reset(), IOW decrement triggered_count. Add the new
reset_control_rearm() call to do so.

When reset_control_reset() has been called once, the counter
triggered_count, in the reset framework, is incremented i.e the resource
under the reset is in-use and the reset should not be done again.
reset_control_rearm() would be the way to state that the resource is
no longer used and, that from the caller's perspective, the reset can be
fired again if necessary.

Signed-off-by: Amjad Ouled-Ameur <aouledameur@baylibre.com>
Reported-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>