serial: 8250_uniphier: fix more unterminated string

Commit 1681d211 ("serial: 8250_uniphier: add "\n" at the end of
error log") missed this.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
[masahiro: add commit log]
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>