utilfdt_read: pass back up the length of data read

For a follow up commit, we want to be able to scan the buffer that was
returned to us.  In order to do that safely, we need to know how big
the buffer actually is, so pass that back if requested.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

util.h

@@ -80,9 +80,10 @@ char get_escape_char(const char *s, int *i);
  * stderr.
  *
  * @param filename	The filename to read, or - for stdin
+ * @param len		If non-NULL, the amount of data we managed to read
  * @return Pointer to allocated buffer containing fdt, or NULL on error
  */
-char *utilfdt_read(const char *filename);
+char *utilfdt_read(const char *filename, off_t *len);
 
 /**
  * Read a device tree file into a buffer. Does not report errors, but only
@@ -91,9 +92,10 @@ char *utilfdt_read(const char *filename);
  *
  * @param filename	The filename to read, or - for stdin
  * @param buffp		Returns pointer to buffer containing fdt
+ * @param len		If non-NULL, the amount of data we managed to read
  * @return 0 if ok, else an errno value representing the error
  */
-int utilfdt_read_err(const char *filename, char **buffp);
+int utilfdt_read_err(const char *filename, char **buffp, off_t *len);
 
 
 /**