part: Drop duplication declaration of block_dev_desc_t

This is already defined in ide.h, which part.h includes. So we don't need
the duplicate typedef. At least with my old blackfin gcc 4.3.5 tool chain,
this causes an error.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>
Reviewed-by: NAndreas Bießmann <andreas.devel@googlemail.com>

include/part.h

@@ -10,8 +10,6 @@
 #include <ide.h>
 #include <common.h>
 
-typedef struct block_dev_desc block_dev_desc_t;
-
 struct block_dev_desc {
 	int		if_type;	/* type of the interface */
 	int		dev;		/* device number */