fpga: bridge: fix obvious function documentation error

fpga_bridge_dev_match() returns a FPGA bridge struct, not a
FPGA manager struct so s/manager/bridge/.

Signed-off-by: Alan Tull <atull@kernel.org>
Acked-by: Moritz Fischer <mdf@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>