serial: Update NS16550_t and struct NS16550

Typedefs should not be used in U-Boot and structs should be lower case.
Update the code to use struct ns16550 consistently.

Put a header guard on the file while we are here.

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

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/board/freescale/p1010rdb/spl.c b/board/freescale/p1010rdb/spl.c
index fbaa6a6..c015a6b 100644
--- a/board/freescale/p1010rdb/spl.c
+++ b/board/freescale/p1010rdb/spl.c
@@ -44,7 +44,7 @@
 	plat_ratio >>= 1;
 	gd->bus_clk = CONFIG_SYS_CLK_FREQ * plat_ratio;
 
-	NS16550_init((NS16550_t)CONFIG_SYS_NS16550_COM1,
+	NS16550_init((struct ns16550 *)CONFIG_SYS_NS16550_COM1,
 		     gd->bus_clk / 16 / CONFIG_BAUDRATE);
 
 #ifdef CONFIG_SPL_MMC_BOOT
diff --git a/board/freescale/p1010rdb/spl_minimal.c b/board/freescale/p1010rdb/spl_minimal.c
index 0bb2c83..4cc70ea 100644
--- a/board/freescale/p1010rdb/spl_minimal.c
+++ b/board/freescale/p1010rdb/spl_minimal.c
@@ -31,8 +31,8 @@
 	plat_ratio >>= 1;
 	gd->bus_clk = CONFIG_SYS_CLK_FREQ * plat_ratio;
 
-	NS16550_init((NS16550_t)CONFIG_SYS_NS16550_COM1,
-			gd->bus_clk / 16 / CONFIG_BAUDRATE);
+	NS16550_init((struct ns16550 *)CONFIG_SYS_NS16550_COM1,
+		     gd->bus_clk / 16 / CONFIG_BAUDRATE);
 
 	puts("\nNAND boot... ");
 
@@ -53,9 +53,9 @@
 void putc(char c)
 {
 	if (c == '\n')
-		NS16550_putc((NS16550_t)CONFIG_SYS_NS16550_COM1, '\r');
+		NS16550_putc((struct ns16550 *)CONFIG_SYS_NS16550_COM1, '\r');
 
-	NS16550_putc((NS16550_t)CONFIG_SYS_NS16550_COM1, c);
+	NS16550_putc((struct ns16550 *)CONFIG_SYS_NS16550_COM1, c);
 }
 
 void puts(const char *str)