fixed mms_dp_gain_serial_arr latency

Closes L2SDP-787

applications/lofar2/libraries/sdp/src/vhdl/sdp_bf_weights.vhd

@@ -120,7 +120,10 @@ BEGIN
     g_gain_w          => c_sdp_W_bf_weight,
     g_in_dat_w        => c_sdp_W_subband,
     g_out_dat_w       => c_gain_out_dat_w,
-    g_gains_file_name => g_gains_file_name
+    g_gains_file_name => g_gains_file_name,
+    -- extra input latency to ease timing.
+    g_pipeline_real_mult_input    => 2, 
+    g_pipeline_complex_mult_input => 2 
   )
   PORT MAP (
     -- System