Locking is done in the same way in _vortex_interrupt() and
_boomerang_interrupt(). To prevent duplication, move the locking into the
calling vortex_boomerang_interrupt() function.

No functional change.

Cc: Steffen Klassert <klassert@mathematik.tu-chemnitz.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>