bnxt: Do not read past the end of test names

In the Linux kernel, the following vulnerability has been resolved: bnxt: Do not read past the end of test names Test names were being concatenated based on a offset beyond the end of the first name, which tripped the buffer overflow detection logic: detected buffer overflow in strnlen [...] Call Trace: bnxt_ethtool_init.cold+0x18/0x18 Refactor struct hwrm_selftest_qlist_output to use an actual array, and adjust the concatenation to use snprintf() rather than a series of strncat() calls.