doc: vfs: fix fadvise() sycall name

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Documentation/filesystems/vfs.txt

@@ -727,7 +727,7 @@ struct address_space_operations {
 
 	The second case is when a request has been made to invalidate
         some or all pages in an address_space.  This can happen
-        through the fadvice(POSIX_FADV_DONTNEED) system call or by the
+        through the fadvise(POSIX_FADV_DONTNEED) system call or by the
         filesystem explicitly requesting it as nfs and 9fs do (when
         they believe the cache may be out of date with storage) by
         calling invalidate_inode_pages2().