Correct returning IRQ_HANDLED unconditionally in the irq handler.
Return IRQ_NONE for some interrupt which we do not expect to be
handled in this handler. This prevents kernel stalling with back
to back spurious interrupts.

Fixes: 2722e56d ("OMAP4: l3: Introduce l3-interconnect error handling driver")
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>