serial: uniphier: move CONFIG_UNIPHIER_SERIAL to Kconfig

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/ph1_ld4_defconfig b/configs/ph1_ld4_defconfig
index c8404f8..e6aba42 100644
--- a/configs/ph1_ld4_defconfig
+++ b/configs/ph1_ld4_defconfig
@@ -7,4 +7,5 @@
 CONFIG_SYS_NAND_DENALI_64BIT=y
 CONFIG_NAND_DENALI_SPARE_AREA_SKIP_BYTES=8
 CONFIG_DM_SERIAL=y
+CONFIG_UNIPHIER_SERIAL=y
 S:CONFIG_SPL_NAND_DENALI=y