pktgen: Fix unsigned function that is returning negative vals

Every call to num_args() immediately checks the return value for
less than zero, as it will return -EFAULT for a failed get_user()
call.  So it makes no sense for the function to be declared as an
unsigned long.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/pktgen.c

@@ -767,8 +767,8 @@ static int count_trail_chars(const char __user * user_buffer,
 	return i;
 }
 
-static unsigned long num_arg(const char __user * user_buffer,
-			     unsigned long maxlen, unsigned long *num)
+static long num_arg(const char __user *user_buffer, unsigned long maxlen,
+				unsigned long *num)
 {
 	int i;
 	*num = 0;