av: avoid driver path truncation

av: avoid driver path truncation

Using strncat() and strncpy() may lead to string truncation, which
might generate other issues.

This patch replaces the usage of strncat() and strncpy() to generate
the driver path, with snprintf() safetly.

See more information here:
https://developers.redhat.com/blog/2018/05/24/detecting-string-truncation-with-gcc-8/