ARM: OMAP2+: Drop omap_hwmod_irq_info

With the previous patches removing the need for legacy IRQs
now that all of mach-omap2 is booting in device tree only mode,
we can drop struct omap_hwmod_irq_info.

Note that we can now also finally drop omap4_xlate_irq.

Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>