board: nuvoton: update console environment variable

If CONFIG_SYS_SKIP_UART_INIT is enabled, calculate the
current baud rate and update the "console" environment
variable.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
diff --git a/board/nuvoton/common/Kconfig b/board/nuvoton/common/Kconfig
new file mode 100644
index 0000000..61de7bc
--- /dev/null
+++ b/board/nuvoton/common/Kconfig
@@ -0,0 +1,9 @@
+if ARCH_NPCM
+
+config SYS_SKIP_UART_INIT
+	bool "Skip UART initialization"
+	depends on NPCM_SERIAL
+	help
+	  Select this if the UART you want to use is already
+	  initialized by the time U-Boot starts its execution.
+endif