The parameter C_SAME_CLKS in the opb2plb_bridge data sheet shows default value of "1" where the opb2plb_bridge_v2_1_0.mpd shows a default value of "0".
in addition, the HDL file (opb2plb_bridge.vhd) has the default for C_SAME_CLKS set to "1", but the MPD file overwrites it to be "0".
There is a discrepancy between the MPD and the Datasheet/HDL. The default value in the MPD is what is being used for the HDL wrapper to the bridge.
You can override this value either in the MHS or the in the MPD file.