pds_fwctl: add rpc and query support

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/20250320194412.67983-6-shannon.nelson@amd.com
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>