imx: Include <input.h> header file

When building with W=1 errors like the one below is seen:

board/freescale/mx6sabresd/mx6sabresd.c:546:5: warning:
no previous prototype for ‘overwrite_console’
[-Wmissing-prototypes] int overwrite_console(void)

Fix the build warnings by including <input.h>.

Signed-off-by: Diego Dorta <diego.dorta@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
diff --git a/board/freescale/mx6sabresd/mx6sabresd.c b/board/freescale/mx6sabresd/mx6sabresd.c
index f14b759..6cc228a 100644
--- a/board/freescale/mx6sabresd/mx6sabresd.c
+++ b/board/freescale/mx6sabresd/mx6sabresd.c
@@ -25,6 +25,7 @@
 #include <asm/io.h>
 #include <asm/arch/sys_proto.h>
 #include <i2c.h>
+#include <input.h>
 #include <power/pmic.h>
 #include <power/pfuze100_pmic.h>
 #include "../common/pfuze.h"