iommu/omap: add pdata ops for omap_device_enable/idle

Add two new platform data ops to allow the OMAP iommu driver to
be able to invoke the omap_device_enable and omap_device_idle
from within the driver. These are being added to streamline the
sequence between managing the hard reset lines and the clocks
during the suspend path, as the default device pm_domain callback
sequences in omap_device layer are not conducive for the OMAP
IOMMU driver.

This could have been done by expanding the existing pdata ops
for reset management (like in the OMAP remoteproc driver), but
this was chosen to avoid adding new code in a separate file in
the mach-omap2 layer.

Signed-off-by: Suman Anna <s-anna@ti.com>