hpfs_setattr error case avoids unlock_kernel

This fixed a case that 'sparse' spotted where hpfs_setattr has an error return
that didn't go through it's path that unlocks.

This is against git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
version 6313e3c21743cc88bb5bd8aa72948ee1e83937b6.

Build tested only, I don't have an hpfs file system to test.

Dave

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>