cmd: nand: Remove not used declaration

This declaration is not used anywhere in the whole tree. There is a
function 'mtd_id_parse()' which was renamed from 'id_parse()' in
commit 68d7d65100 ("Separate mtdparts command from jffs2"), but that
function is not used (anymore?) in cmd nand and build is fine without
that declaration, so it's probably just safe to remove.

Signed-off-by: Alexander Dahl <ada@thorsis.com>

cmd/nand.c

@@ -34,7 +34,6 @@
 
 /* partition handling routines */
 int mtdparts_init(void);
-int id_parse(const char *id, const char **ret_id, u8 *dev_type, u8 *dev_num);
 int find_dev_and_part(const char *id, struct mtd_device **dev,
 		      u8 *part_num, struct part_info **part);
 #endif