scsi: qla2xxx: Avoid possible run-time warning with long model_num

The prior strlcpy() replacement of strncpy() here (which was
later replaced with strscpy()) expected pinfo->model_num (and
pinfo->model_description) to be NUL-terminated, but it is possible
it was not, as the code pattern here shows vha->hw->model_number (and
vha->hw->model_desc) being exactly 1 character larger, and the replaced
strncpy() was copying only up to the size of the source character
array. Replace this with memtostr(), which is the unambiguous way to
convert a maybe not-NUL-terminated character array into a NUL-terminated
string.

Fixes: 527e9b70

 ("scsi: qla2xxx: Use memcpy() and strlcpy() instead of strcpy() and strncpy()")
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240410023155.2100422-5-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>