ARM: OMAP4+: PRM: get rid of cpu_is_omap44xx calls from interrupt init

The compatible DT node is now passed with the prm init, so there is no
need to do node matching here again. Added a new flag to the init data
also, to detect default IRQ support for OMAP4. Also, any booting omap4
DT setup always has a PRM node, so there is no need to check against
the special case where it would be missing.

Signed-off-by: Tero Kristo <t-kristo@ti.com>