powerpc/powernv: Free name on error in opal_event_init()

In opal_event_init() if request_irq() fails name is not freed, leading
to a memory leak. The code only runs at boot time, there's no way for a
user to trigger it, so there's no security impact.

Fix the leak by freeing name in the error path.

Reported-by: 2639161967 <2639161967@qq.com>
Closes: https://lore.kernel.org/linuxppc-dev/87wmjp3wig.fsf@mail.lhotse


Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20240920093520.67997-1-mpe@ellerman.id.au