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/bf527-ezkit_defconfig b/configs/bf527-ezkit_defconfig
index 8752267..7638550 100644
--- a/configs/bf527-ezkit_defconfig
+++ b/configs/bf527-ezkit_defconfig
@@ -2,5 +2,5 @@
 CONFIG_TARGET_BF527_EZKIT=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_NET_RANDOM_ETHADDR=y
+# CONFIG_NET_TFTP_VARS is not set
 CONFIG_SPI_FLASH=y
-CONFIG_NET_TFTP_VARS=n