net: remove obsolete simple_strto<foo>

This patch replace the obsolete simple_strto<foo> with kstrto<foo>

Signed-off-by: Abhijit Pawar <abhi.c.pawar@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>