Staging: comedi: kcomedilib: replace deprecated simple_strtoul() with kstrtouint()

Since simple_strtoul() has been deprecated, replace it with kstrtouint().
Also, since return code checking for this new function is enforced, add a
check to ensure that the conversion has succeeded.

Signed-off-by: Chase Southwood <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/comedi/kcomedilib/kcomedilib_main.c

···
 	if (strncmp(filename, "/dev/comedi", 11) != 0)
 		return NULL;
 
-	minor = simple_strtoul(filename + 11, NULL, 0);
+	if (kstrtouint(filename + 11, 0, &minor))
+		return NULL;
 
 	if (minor >= COMEDI_NUM_BOARD_MINORS)
 		return NULL;