drm/msm: add missing header dependencies

We get 2 warnings when building kernel with W=1:
drivers/gpu/drm/msm/msm_debugfs.c:141:5: warning: no previous prototype for 'msm_debugfs_init' [-Wmissing-prototypes]
drivers/gpu/drm/msm/msm_debugfs.c:158:6: warning: no previous prototype for 'msm_debugfs_cleanup' [-Wmissing-prototypes]

In fact, these functions are declared in
drivers/gpu/drm/msm/msm_debugfs.h.
So this patch adds missing header dependencies.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1477127865-9381-2-git-send-email-baoyou.xie@linaro.org

drivers/gpu/drm/msm/msm_debugfs.c

@@ -18,6 +18,7 @@
 #ifdef CONFIG_DEBUG_FS
 #include "msm_drv.h"
 #include "msm_gpu.h"
+#include "msm_debugfs.h"
 
 static int msm_gpu_show(struct drm_device *dev, struct seq_file *m)
 {