[ARM] 4450/1: pxa: add pxa25x_init_irq() and pxa27x_init_irq()

/* should be ok this time, I aligned this patch to your arm:pxa2.mbox */

1. move pxa25x specific IRQ initialization code to pxa25x_init_irq()
and pxa27x code to pxa27x_init_irq(), remove pxa_init_irq()

2. replace all pxa_init_irq() with their PXA25x or PXA27x specific
functions

Signed-off-by: eric miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>