Fix typo

Signed-off-by: François Revol <revol@free.fr>

libfdt/libfdt.h

@@ -582,7 +582,7 @@ const char *fdt_get_alias_namelen(const void *fdt,
  * value of the property named 'name' in the node /aliases.
  *
  * returns:
- *	a pointer to the expansion of the alias named 'name', of it exists
+ *	a pointer to the expansion of the alias named 'name', if it exists
  *	NULL, if the given alias or the /aliases node does not exist
  */
 const char *fdt_get_alias(const void *fdt, const char *name);