m68k/atari: Add missing platform check before registering platform devices

On multi-platform kernels, the Atari platform devices should be registered
when running on Atari only. Else it may crash later.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
diff --git a/arch/m68k/atari/config.c b/arch/m68k/atari/config.c
index 4dba411..4fc7396 100644
--- a/arch/m68k/atari/config.c
+++ b/arch/m68k/atari/config.c
@@ -692,6 +692,9 @@
 
 int __init atari_platform_init(void)
 {
+	if (!MACH_IS_ATARI)
+		return -ENODEV;
+
 	return platform_add_devices(atari_platform_devices, ARRAY_SIZE(atari_platform_devices));
 }