Documentation/filesystems/porting fixes

typo fix and whitespace cleanup
Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

Documentation/filesystems/porting

@@ -28,7 +28,7 @@ Declare
 
 Use FOO_I(inode) instead of &inode->u.foo_inode_i;
 
-Add foo_alloc_inode() and foo_destory_inode() - the former should allocate
+Add foo_alloc_inode() and foo_destroy_inode() - the former should allocate
 foo_inode_info and return the address of ->vfs_inode, the latter should free
 FOO_I(inode) (see in-tree filesystems for examples).