ARM: 6048/1: ARM: iop3xx: register PMU IRQs during board initialisation

This patch adds an initcall for the iop3xx platforms so that they
register their PMU IRQS with the PMU framework in the Kernel.

Cc: Lennert Buytenhek <kernel@wantstofly.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>