board: freescale: imxrt10..-evk: Fix missing include of serial.h

If FALCON mode is enabled we have a missing include in spl_start_uboot.

Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
diff --git a/board/freescale/imxrt1020-evk/imxrt1020-evk.c b/board/freescale/imxrt1020-evk/imxrt1020-evk.c
index 54a733b..785da60 100644
--- a/board/freescale/imxrt1020-evk/imxrt1020-evk.c
+++ b/board/freescale/imxrt1020-evk/imxrt1020-evk.c
@@ -13,6 +13,7 @@
 #include <asm/global_data.h>
 #include <asm/io.h>
 #include <asm/armv7m.h>
+#include <serial.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
diff --git a/board/freescale/imxrt1050-evk/imxrt1050-evk.c b/board/freescale/imxrt1050-evk/imxrt1050-evk.c
index 6132916..4b82ee5 100644
--- a/board/freescale/imxrt1050-evk/imxrt1050-evk.c
+++ b/board/freescale/imxrt1050-evk/imxrt1050-evk.c
@@ -13,6 +13,7 @@
 #include <asm/global_data.h>
 #include <asm/io.h>
 #include <asm/armv7m.h>
+#include <serial.h>
 
 DECLARE_GLOBAL_DATA_PTR;