ubi: pr_err() strings should end with newlines

The ubi_init() function has a few error paths that use the
pr_err() to output errors. These should have new lines on
them as pr_err() does not automatically do this.

This fixes issues where if multiple mtd fail to bind to
ubi the console output starts wrapping around.

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