serial: Use default_serial_puts() in drivers

Replace the in-place ad-hoc implementation of serial_puts() within
the drivers with default_serial_puts() call. This cuts down on the
code duplication quite a bit.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Tom Rini <trini@ti.com>
diff --git a/board/cogent/serial.c b/board/cogent/serial.c
index cd4a976..20631d1 100644
--- a/board/cogent/serial.c
+++ b/board/cogent/serial.c
@@ -68,12 +68,6 @@
 	cma_mb_reg_write (&mbsp->ser_thr, c);
 }
 
-static void cogent_serial_puts(const char *s)
-{
-	while (*s != '\0')
-		serial_putc (*s++);
-}
-
 static int cogent_serial_getc(void)
 {
 	cma_mb_serial *mbsp = (cma_mb_serial *) CMA_MB_SERIAL_BASE;
@@ -96,7 +90,7 @@
 	.stop	= NULL,
 	.setbrg	= cogent_serial_setbrg,
 	.putc	= cogent_serial_putc,
-	.puts	= cogent_serial_puts,
+	.puts	= default_serial_puts,
 	.getc	= cogent_serial_getc,
 	.tstc	= cogent_serial_tstc,
 };