libfdt: Remove unused _ptr_offset() function

The (internal use) function _ptr_offset() is never used.  Delete it.

libfdt_internal.h

@@ -26,13 +26,6 @@
 #define memeq(p, q, n)	(memcmp((p), (q), (n)) == 0)
 #define streq(p, q)	(strcmp((p), (q)) == 0)
 
-static inline int _ptr_offset(struct fdt_header *fdt, void *p)
-{
-	void *blob = fdt;
-
-	return (p - blob) - fdt_off_dt_struct(fdt);
-}
-
 int _fdt_check_header(const struct fdt_header *fdt);
 uint32_t _fdt_next_tag(const struct fdt_header *fdt, int startoffset, int *nextoffset);
 const char *_fdt_find_string(const char *strtab, int tabsize, const char *s);