power: reset: ltc2952: cleanup control flow in poweroff_handler

ltc2952_poweroff_handler uses gotos to return from the function. Since
we don't do cleanups exiting this function, just return IRQ_HANDLED on
the spot and be done with it.

While at it, remove the variable 'ret'. It was never used very much.

Signed-off-by: Frans Klaver <frans.klaver@xsens.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>