atm: solos-pci: Replace simple_strtol by kstrtoint

The simple_strtol function is obsolete.
This patch replace it by kstrtoint.
This will simplify code, since some error case not handled by
simple_strtol are handled by kstrtoint.

Signed-off-by: LABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>