ARM: dts: Configure pmu without interrupt for omap4430

On omap4430, the PMU is not configure unlike on omap4460 because
of the missing handling.

The missing pmu node with the missing ti,hwmods entry will cause
boot time errors when the legacy platform data is removed as
the SoC interconnect code needs it.

Note that this will only show up as a bug with "doesn't have
mpu register target base" boot errors when the legacy platform
data is removed.

Let's fix the issue by configuring PMU but without the interrupts.
Then when cross trigger interface (CTI) is supported, we can add
interrupts also for omap4430.

Cc: Jon Hunter <jonathanh@nvidia.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>