ns16550: move CONFIG_SYS_NS16550 to Kconfig

Move CONFIG_SYS_NS16550 to Kconfig, and run moveconfig.py.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
diff --git a/configs/yellowstone_defconfig b/configs/yellowstone_defconfig
index 7b1a630..7f4144c 100644
--- a/configs/yellowstone_defconfig
+++ b/configs/yellowstone_defconfig
@@ -2,3 +2,4 @@
 CONFIG_4xx=y
 CONFIG_TARGET_YOSEMITE=y
 CONFIG_SYS_EXTRA_OPTIONS="YELLOWSTONE"
+CONFIG_SYS_NS16550=y