pds_fwctl: add rpc and query support

The pds_fwctl driver doesn't know what RPC operations are available
in the firmware, so also doesn't know what scope they might have.  The
userland utility supplies the firmware "endpoint" and "operation" id values
and this driver queries the firmware for endpoints and their available
operations.  The operation descriptions include the scope information
which the driver uses for scope testing.

Link: https://patch.msgid.link/r/[email protected]
Reviewed-by: Leon Romanovsky <[email protected]>
Signed-off-by: Brett Creeley <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Signed-off-by: Shannon Nelson <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: brettcreeley