dm: Tidy up four minor code nits

There is a spelling mistake and two functions are missing comments
altogether. Also the flags declaration is correct, but doesn't follow
style. Finally, the uclass_get_device() function has some errors in
its documentation.

Fix these problems.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Marek Vasut <marex@denx.de>

include/dm/device.h

@@ -21,7 +21,7 @@ struct driver_info;
 #define DM_FLAG_ACTIVATED	(1 << 0)
 
 /* DM is responsible for allocating and freeing platdata */
-#define DM_FLAG_ALLOC_PDATA	(2 << 0)
+#define DM_FLAG_ALLOC_PDATA	(1 << 1)
 
 /**
  * struct udevice - An instance of a driver