global: Move remaining CONFIG_SYS_NS16550_* to CFG_SYS_NS16550_*

The rest of the unmigrated CONFIG symbols in the CONFIG_SYS_NS16550
namespace do not easily transition to Kconfig. In many cases they likely
should come from the device tree instead. Move these out of CONFIG
namespace and in to CFG namespace.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 4978a65..14b0feb 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -737,7 +737,7 @@
 	  Support NS16550 UART or compatible. This can be enabled in the
 	  device tree with the correct input clock frequency. If the input
 	  clock frequency is not defined in the device tree, the macro
-	  CONFIG_SYS_NS16550_CLK defined in a legacy board header file will
+	  CFG_SYS_NS16550_CLK defined in a legacy board header file will
 	  be used. It can be a constant or a function to get clock, eg,
 	  get_serial_clock().