drivers: serial: ns16550: move header from /include/

Move ns16550 to the driver directory. No other users in the tree and it
is a private header.

Signed-off-by: Anas Nashif <[email protected]>

Author: nashif

drivers/serial/uart_ns16550.c

@@ -32,7 +32,7 @@
 #include <uart.h>
 #include <sys_io.h>
 
-#include <drivers/serial/uart_ns16550.h>
+#include "uart_ns16550.h"
 
 /*
  * If PCP is set for any of the ports, enable support.