staging: speakup: fix misuse of kstrtol() in handle_goto()

A string of goto_buf has a number followed by x or y.
e.g. "3x" means move 3 lines down.
The kstrtol() returns an error(-EINVAL) with this string so
go_pos has unsigned a value of that error.
And also "*cp" has not expected value.

And fix sparse warnings:
 drivers/staging/speakup/main.c:1901 handle_goto() warn: unsigned '(speakup_console[vc->vc_num]->go_pos)' is never less than zero.
 drivers/staging/speakup/main.c:1911 handle_goto() warn: unsigned '(speakup_console[vc->vc_num]->go_pos)' is never less than zero.
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/main.c

@@ -1855,8 +1855,9 @@ static int handle_goto(struct vc_data *vc, u_char type, u_char ch, u_short key)
 {
 	static u_char goto_buf[8];
 	static int num;
-	int maxlen, go_pos;
+	int maxlen;
 	char *cp;
+
 	if (type == KT_SPKUP && ch == SPEAKUP_GOTO)
 		goto do_goto;
 	if (type == KT_LATIN && ch == '\n')
@@ -1891,25 +1892,24 @@ static int handle_goto(struct vc_data *vc, u_char type, u_char ch, u_short key)
 		spk_special_handler = NULL;
 		return 1;
 	}
-	go_pos = kstrtol(goto_buf, 10, (long *)&cp);
-	goto_pos = (u_long) go_pos;
+
+	goto_pos = simple_strtoul(goto_buf, &cp, 10);
+
 	if (*cp == 'x') {
 		if (*goto_buf < '0')
 			goto_pos += spk_x;
-		else
+		else if (goto_pos > 0)
 			goto_pos--;
-		if (goto_pos < 0)
-			goto_pos = 0;
+
 		if (goto_pos >= vc->vc_cols)
 			goto_pos = vc->vc_cols - 1;
 		goto_x = 1;
 	} else {
 		if (*goto_buf < '0')
 			goto_pos += spk_y;
-		else
+		else if (goto_pos > 0)
 			goto_pos--;
-		if (goto_pos < 0)
-			goto_pos = 0;
+
 		if (goto_pos >= vc->vc_rows)
 			goto_pos = vc->vc_rows - 1;
 		goto_x = 0;