nvme-fabrics: fix DHCHAP secret leak on parse failure

In the Linux kernel, the following vulnerability has been resolved: nvme-fabrics: fix DHCHAP secret leak on parse failure nvmf_parse_options() duplicates dhchap_secret and dhchap_ctrl_secret with match_strdup() before validating the DHHC-1: representation. If validation fails, the parser returns -EINVAL before the temporary string in p is assigned to opts->dhchap_secret or opts->dhchap_ctrl_secret. nvmf_create_ctrl() subsequently frees opts, but nvmf_free_options() cannot release the unassigned temporary string. Each rejected option therefore leaks one allocation. This is easy to miss because valid secrets transfer ownership to opts and are freed normally, while the malformed-secret path still returns the expected -EINVAL to userspace. With CONFIG_NVME_HOST_AUTH enabled, the leak is reachable before the required-option checks and transport lookup. No NVMe-oF target or working transport connection is required; for example, repeatedly writing dhchap_secret=BAD or dhchap_ctrl_secret=BAD to /dev/nvme-fabrics deterministically takes the leaking parse path. Free the temporary string before leaving both validation error paths. Use kfree_sensitive() because the copied option may contain secret material even when its representation is rejected, matching the sensitive cleanup used for stored DHCHAP secrets.