fb: mmp: include linux/platform_device.h

Commit 16559ae48c76 ("kgdb: remove #include <linux/serial_8250.h> from
kgdb.h") changes the kgdb.h file so that drivers including it do not
implicitly include linux/platform_device.h. The mmp framebuffer driver
is new, so Greg did not have a chance to fix it up when introducing his
change.

Signed-off-by: Arnd Bergmann <[e-mail]>
Cc: Zhou Zhu <[e-mail]>
Cc: Lisa Du <[e-mail]>
Cc: Guoqing Li <[e-mail]>
Acked-by: Haojian Zhuang <[e-mail]>
Cc: Florian Tobias Schandinat <[e-mail]>
Cc: Greg KH <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/mmp/fb/mmpfb.c

···
  */
 #include <linux/module.h>
 #include <linux/dma-mapping.h>
+#include <linux/platform_device.h>
 #include "mmpfb.h"
 
 static int var_to_pixfmt(struct fb_var_screeninfo *var)