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/drivers/power/domain/imx8-power-domain.c b/drivers/power/domain/imx8-power-domain.c
index 17b5d57..b45e468 100644
--- a/drivers/power/domain/imx8-power-domain.c
+++ b/drivers/power/domain/imx8-power-domain.c
@@ -10,7 +10,7 @@
 #include <malloc.h>
 #include <power-domain-uclass.h>
 #include <asm/arch/power-domain.h>
-#include <asm/arch/sci/sci.h>
+#include <firmware/imx/sci/sci.h>
 
 static int imx8_power_domain_on(struct power_domain *power_domain)
 {