power: reset: ltc2952: prefer devm_request_irq over request_irq

Make use of the fact that we allocated resources can be automatically
deallocated. This reduces cleanup code and chance of errors. It also
removes the need for the virq member of the ltc2952_poweroff_data
struct.

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