UPSTREAM: tty: serial: samsung_tty: fix build warning

Fix a build warning on systems that do not have CONFIG_OF enabled.

Bug: 144661360
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Hyunki Koo <kkoos00@naver.com>
Cc: HYUN-KI KOO <hyunki00.koo@samsung.com>
Cc: Shinbeom Choi <sbeom.choi@samsung.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20191210143706.3928480-2-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 06674e54cc412c47cc2b909cb06c85521999763c)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Id1c9c66aaf95a97437318e8a6156bc3d2ab7040d