tools: specify buffer to be size PATH_MAX

tools: specify buffer to be size PATH_MAX

Using a CodeQL query, I discovered that the destination of a `sscanf` call could overflow.
Thus, we bound the buffer size to be PATH_MAX, to ensure that it is
not larger than `modname` or `devname`.

Signed-off-by: Grayson Nocera <gnocera@purdue.edu>
Suggested-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/260
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>