OMAP: Fix a BUG in l3 error handler.

With the current sequence of registering the irq and
assigning it to the app_irq, debug_irq driver variables,
there can be corner cases where the pending irq gets
triggered immediately after registering, handler gets called
resulting in a crash. So changed this sequence.

Signed-off-by: sricharan <r.sricharan@ti.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>