ARM: keystone2: Fix serial port init

With CONFIG_DM_SERIAL is enabled NS16550_init() cannot be
called directly. Driver probe should be taking care of this.
So call this function only when DM_SERIAL is not enabled.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/arch/arm/mach-keystone/init.c b/arch/arm/mach-keystone/init.c
index a9a7d41..678afb1 100644
--- a/arch/arm/mach-keystone/init.c
+++ b/arch/arm/mach-keystone/init.c
@@ -122,8 +122,10 @@
 	 * UART register PWREMU_MGMT is initialized. Linux UART
 	 * driver doesn't handle this.
 	 */
+#ifndef CONFIG_DM_SERIAL
 	NS16550_init((NS16550_t)(CONFIG_SYS_NS16550_COM2),
 		     CONFIG_SYS_NS16550_CLK / 16 / CONFIG_BAUDRATE);
+#endif
 
 	return 0;
 }