docs: fpga: document fpga manager flags

Add flags #defines to kerneldoc documentation in a
useful place.

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

Documentation/driver-api/fpga/fpga-mgr.rst

@@ -184,6 +184,11 @@ API for implementing a new FPGA Manager driver
 API for programming an FPGA
 ---------------------------
 
+FPGA Manager flags
+
+.. kernel-doc:: include/linux/fpga/fpga-mgr.h
+   :doc: FPGA Manager flags
+
 .. kernel-doc:: include/linux/fpga/fpga-mgr.h
    :functions: fpga_image_info