serial: Rename ns16550 functions to lower case

Lower case should be used for function names. Update this driver and its
callers accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/board/freescale/t102xrdb/spl.c b/board/freescale/t102xrdb/spl.c
index d23b2f5..66d2f3b 100644
--- a/board/freescale/t102xrdb/spl.c
+++ b/board/freescale/t102xrdb/spl.c
@@ -82,7 +82,7 @@
 	plat_ratio = (in_be32(&gur->rcwsr[0]) >> 25) & 0x1f;
 	ccb_clk = sys_clk * plat_ratio / 2;
 
-	NS16550_init((struct ns16550 *)CONFIG_SYS_NS16550_COM1,
+	ns16550_init((struct ns16550 *)CONFIG_SYS_NS16550_COM1,
 		     ccb_clk / 16 / CONFIG_BAUDRATE);
 
 #if defined(CONFIG_SPL_MMC_BOOT)