ARM: OMAP: make wakeupgen_lock raw

When applying RT patch on top of Linux, spinlocks are
implemented as RT-mutexes, which means they are preemptable.

Current GIC implementation on OMAP is using a spinlock
to protect against preemption. As it turns out, we need
to convert that lock into a raw_spinlock so that OMAP's
interrupt controller works as expected after RT-patch
is applied.

This patch is simply to decrease the amount of changes
RT-team needs to carry out of tree. It doesn't cause any
changes in behavior.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>