ARM: omap2+: board-generic: clean up the irq data from board file

Move the irq_match arrays and the irq init functions of OMAP 2,3
and 4 based boards out of board-generic.c file and also rename the
irq init function to match the interrupt controller present in
the SOCs.

This is a preparatory patch to add the OMAP5 evm board's irq init
support with device tree.

Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>