Dove: Fix irq_to_pmu()

PMU interrupts start at IRQ_DOVE_PMU_START, not IRQ_DOVE_PMU_START + 1.
Fix the condition.  (It may have been less likely to occur had the code
been written "if (irq >= IRQ_DOVE_PMU_START" which imho is the easier
to understand notation, and matches the normal way of thinking about
these things.)

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Jason Cooper <jason@lakedaemon.net>