Input: amijoy - add missing platform check

On multi-platform kernels, the Amiga joystick driver may be initialized
when running on Amiga only. Else it may crash later.
Fortunately this driver is almost always compiled as a module (to avoid
conflicts with the mouse driver), so it needs an explicit insmod to
trigger a crash.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/joystick/amijoy.c

···
 	int i, j;
 	int err;
 
+	if (!MACH_IS_AMIGA)
+		return -ENODEV;
+
 	for (i = 0; i < 2; i++) {
 		if (!amijoy[i])
 			continue;