cmd_parser.c conflicted twice: main rewrote the pvid command around the
new port-separator and atoi helpers, next to the line where this branch
delegates "stp" to stp_parse(). Both belong, so the STP delegation keeps
main's pvid body.
The linker caught what the merge could not see: main changed atoi_byte()
to return the digit count and leave the value in atoi_results_u8, where
it used to return non-zero on failure and write through a pointer. Note
the sense is inverted, so the three calls in rtl837x_stp.c are adjusted
rather than just re-arranged.