ADB: Add missing #include <linux/platform_device.h>

Commit c9f6d3d5 ("[POWERPC] adb: Replace
sleep notifier with platform driver suspend/resume hooks") introduced
compile errors on m68k because <linux/platform_device.h> is not
explicitly included.  On powerpc, it's pulled in through <asm/prom.h>.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/macintosh/adb.c

@@ -36,6 +36,7 @@
 #include <linux/completion.h>
 #include <linux/device.h>
 #include <linux/kthread.h>
+#include <linux/platform_device.h>
 
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>