ARM: dts: Fix smartreflex compatible for omap3 shared mpu-iva instance

The smartreflex instance for mpu and iva is shared. Let's fix this as I've
already gotten confused myself few times wondering where the mpu instance
is. Note that we are still probing the driver using platform data so this
change is safe to do.

Signed-off-by: Tony Lindgren <tony@atomide.com>