powerpc/xive: Remove irqd_is_started() check when setting the affinity

In the early days of XIVE support, commit cffb717c ("powerpc/xive:
Ensure active irqd when setting affinity") tried to fix an issue
related to interrupt migration. If the root cause was related to CPU
unplug, it should have been fixed and there is no reason to keep the
irqd_is_started() check. This test is also breaking affinity setting
of MSIs which can set before starting the associated IRQ.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210701132750.1475580-8-clg@kaod.org