ARM: OMAP2+: Prepare for device-tree PMU support

If device-tree is present, then do not create the PMU device from within
the OMAP specific PMU code. This is required to allow device-tree to
create the PMU device from the PMU device-tree node.

PMU is not currently supported for OMAP4430 (due to a dependency on
having a cross-trigger interface driver) and so ensure that this
indicated on boot with or without device-tree.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
ARM: dts: OMAP2+: Add PMU nodes

Add PMU nodes for OMAP2, OMAP3 and OMAP4460 devices.

Please note that the node for OMAP4460 has been placed in a separate
header file for OMAP4460, because the node is not compatible with
OMAP4430. The node for OMAP4430 is not included because PMU is not
currently supported on OMAP4430 due to the absence of a cross-trigger
interface driver.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
ARM: dts: AM33xx: Add PMU node

Add PMU node for AM33xx devices.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>