ubi: pr_err() strings should end with newlines

In ubi_attach_mtd_dev() the pr_err() calls should have their
messgaes terminated with a new-line to avoid other messages
being concatenated onto the end.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>