libfdt: Add functions to get/add/delete memory reservemap entries

This patch adds functions to libfdt for accessing the memory
reservation map section of a device tree blob.  fdt_num_mem_rsv()
retreives the number of reservation entries in a dtb, and
fdt_get_mem_rsv() retreives a specific reservation entry.
fdt_add_mem_rsv() adds a new entry, and fdt_del_mem_rsv() removes a
specific numbered entry.

Testcases for these new functions are also included.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/tests.h

@@ -108,6 +108,8 @@ static inline void *xrealloc(void *p, size_t size)
 	return p;
 }
 
+void check_mem_rsv(void *fdt, int n, uint64_t addr, uint64_t size);
+
 void check_property(void *fdt, int nodeoffset, const char *name,
 		    int len, const void *val);
 #define check_property_typed(fdt, nodeoffset, name, val) \