anv: use snprintf() instead of memset()+strcpy()

anv: use snprintf() instead of memset()+strcpy()

snprintf() guarantees that it will not write more chars than allowed,
and that the string will be null-terminated, without the need to fill
the whole thing with zeroes to begin with.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>