imx: add Kconfig entry for i.MX8QXP

Add Kconfig entry for i.MX8QXP

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/mach-imx/Makefile b/arch/arm/mach-imx/Makefile
index 9b00074..d6dcbe0 100644
--- a/arch/arm/mach-imx/Makefile
+++ b/arch/arm/mach-imx/Makefile
@@ -143,3 +143,4 @@
 obj-$(CONFIG_MX7) += mx7/
 obj-$(CONFIG_ARCH_MX7ULP) += mx7ulp/
 obj-$(CONFIG_MX8M) += mx8m/
+obj-$(CONFIG_ARCH_IMX8) += imx8/