bus/dpaa: support hotplug ops

bus/dpaa: support hotplug ops

Parse and find_device have specific function - former is for parsing a
string passed as argument, whereas the later is for iterating over all
the devices in the bus and calling a callback/handler. They have been
corrected with their right operations to support hotplugging/devargs
plug/unplug calls.

Support for plug/unplug too has been added.

Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>