dpt_i2o: Fix typo of EINVAL

Commit ef7562b7 ("dpt_i2o: Fix up
copy*user") had a silly typo: EINVAL should be -EINVAL.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: stable@kernel.org
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>