Need to document that `SEG` mode argument is available for SDO upload tool.

[follower]

The "SEG" argument here:

libcanopen/bin/rs-canopen-sdo-upload.c

Line 76 in 6e4758b

if (argc == 6 && strcmp(argv[5], "SEG") == 0)

Is not documented as available here:

libcanopen/bin/rs-canopen-sdo-upload.c

Line 52 in 6e4758b

fprintf(stderr, "usage: %s can-interface NODE INDEX SUBINDEX\n", argv[0]);

The existence of the equivalent argument is (somewhat) documented here for the download tool:

libcanopen/bin/rs-canopen-sdo-download.c

Line 51 in 6e4758b

fprintf(stderr, "usage: %s can-interface NODE INDEX SUBINDEX DATA [MODE]\n", argv[0]);

Effect

Without the SEG argument documented it's not clear that e.g. visible strings longer than an expedited transfer can handle are still able to be viewed, e.g.:

$ rs-canopen-sdo-upload can0 30 0x1008 0
0000000b
$ rs-canopen-sdo-upload can0 30 0x1008 0 SEG
43414e6f70656e4e6f6465 // 'C', 'A', 'N', 'o', 'p', 'e', 'n', 'N', 'o', 'd', 'e'