vga_switcheroo: comparing too few characters in strncmp()

This is a copy-and-paste bug.  We should be comparing 4 characters here
instead of 3.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/vga/vga_switcheroo.c

@@ -346,11 +346,11 @@ vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
 	if (strncmp(usercmd, "DIS", 3) == 0)
 		client_id = VGA_SWITCHEROO_DIS;
 
-	if (strncmp(usercmd, "MIGD", 3) == 0) {
+	if (strncmp(usercmd, "MIGD", 4) == 0) {
 		just_mux = true;
 		client_id = VGA_SWITCHEROO_IGD;
 	}
-	if (strncmp(usercmd, "MDIS", 3) == 0) {
+	if (strncmp(usercmd, "MDIS", 4) == 0) {
 		just_mux = true;
 		client_id = VGA_SWITCHEROO_DIS;
 	}