Clarified hdr_field_sel bit selects for e.g. udp_checksum.

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

@@ -219,6 +219,7 @@ PACKAGE sdp_pkg is
 
   CONSTANT c_sdp_stat_version_id        : NATURAL := 5;
   CONSTANT c_sdp_stat_nof_hdr_fields    : NATURAL := 1+3+12+4+20+1; -- 608b; 19 32b words
+
   -- hdr_field_sel bit selects where the hdr_field value is set:
   -- . 0 = data path controlled, value is set in sdp_statistics_offload.vhd, so field_default() is not used.
   -- . 1 = MM controlled, value is set via MM or by the field_default(), so any data path setting in
@@ -230,8 +231,9 @@ PACKAGE sdp_pkg is
   --   could still be changed via MM without having to recompile the FW.
   -- . Typically only use data path controlled if the value has to be set dynamically, so dependent
   --   on the state of the FW.
-  -- . If a data path controlled field is not set in the FW, then it defaults to 0, e.g. udp_checksum,
-  --   so this is equivalent to using MM controlled and field_default(0).
+  -- . If a data path controlled field is not set in the FW, then it defaults to 0 by declaring
+  --   hdr_fields_in_arr with all 0. Hence e.g. udp_checksum = 0 can be achieve via data path
+  --   and default hdr_fields_in_arr = 0 or via MM controlled and field_default(0).
   --                                                                                                     eth   ip             udp    app
   CONSTANT c_sdp_stat_hdr_field_sel     : STD_LOGIC_VECTOR(c_sdp_stat_nof_hdr_fields-1 DOWNTO 0) := "1"&"101"&"111011111001"&"0100"&"0100"&"000000010"&"1000000"&"0";  -- current
 --CONSTANT c_sdp_stat_hdr_field_sel     : STD_LOGIC_VECTOR(c_sdp_stat_nof_hdr_fields-1 DOWNTO 0) := "1"&"101"&"111011111001"&"0101"&"0100"&"000000000"&"0000100"&"0";  -- previous 26 nov 2021