Documentation: dt: update omap remoteproc binding for suspend

The OMAP remoteproc binding has been updated to add an additional
property, "ti,rproc-standby-info". The property is used to define
the standby register address required by the OMAP remoteproc driver
to check that a remote proessor has entered standby and ready to
be suspended during a system suspend or a runtime auto-suspend of
the corresponding remoteproc device.

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