genirq/migration: Avoid out of line call if pending is not set

The upcoming fix for the -EBUSY return from affinity settings requires to
use the irq_move_irq() functionality even on irq remapped interrupts. To
avoid the out of line call, move the check for the pending bit into an
inline helper.

Preparatory change for the real fix. No functional change.

Fixes: dccfe314 ("x86/vector: Simplify vector move cleanup")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <liu.song.a23@gmail.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: stable@vger.kernel.org
Cc: Mike Travis <mike.travis@hpe.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Dou Liyang <douly.fnst@cn.fujitsu.com>
Link: https://lkml.kernel.org/r/20180604162224.471925894@linutronix.de