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/whistler_defconfig b/configs/whistler_defconfig
index 995cf36..9fa9664 100644
--- a/configs/whistler_defconfig
+++ b/configs/whistler_defconfig
@@ -12,6 +12,7 @@
 CONFIG_CMD_GPIO=y
 # CONFIG_CMD_SETEXPR is not set
 # CONFIG_CMD_NFS is not set
+CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_DM_USB=y
 CONFIG_USE_PRIVATE_LIBGCC=y