imx: move imx8 sci header file to include/firmware/imx

Move imx8 sci header file to include/firmware/imx, then we could
use build macro to reuse some i.MX8 drivers for i.MX9, such as
drivers/cpu/imx8_cpu.c.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/mach-imx/imx8/fdt.c b/arch/arm/mach-imx/imx8/fdt.c
index a132ce2..02b3ee5 100644
--- a/arch/arm/mach-imx/imx8/fdt.c
+++ b/arch/arm/mach-imx/imx8/fdt.c
@@ -5,7 +5,7 @@
 
 #include <common.h>
 #include <log.h>
-#include <asm/arch/sci/sci.h>
+#include <firmware/imx/sci/sci.h>
 #include <asm/arch/sys_proto.h>
 #include <asm/global_data.h>
 #include <dm/ofnode.h>