mtd: let include/linux/mtd/partitions.h stand on its own

When declaring static MTD partitions in board specific code, only
including <include/linux/mtd/partitions.h> should suffice without
gcc nagging us with:

In file included from arch/arm/mach-kirkwood/sheevaplug-setup.c:14:
include/linux/mtd/partitions.h:50: warning: 'struct mtd_info' declared inside parameter list
include/linux/mtd/partitions.h:50: warning: its scope is only this definition or declaration, which is probably not what you want
include/linux/mtd/partitions.h:51: warning: 'struct mtd_info' declared inside parameter list
include/linux/mtd/partitions.h:61: warning: 'struct mtd_info' declared inside parameter list
include/linux/mtd/partitions.h:67: warning: 'struct mtd_info' declared inside parameter list

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/mtd/partitions.h

@@ -47,6 +47,8 @@ struct mtd_partition {
 #define MTDPART_SIZ_FULL	(0)
 
 
+struct mtd_info;
+
 int add_mtd_partitions(struct mtd_info *, const struct mtd_partition *, int);
 int del_mtd_partitions(struct mtd_info *);