imx8qxp: add SUPPORT_SPL option

Enable SUPPORT_SPL option for i.MX8QXP, then we could enable SPL.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/imx8/Kconfig b/arch/arm/mach-imx/imx8/Kconfig
index 0d3a87c..9671107 100644
--- a/arch/arm/mach-imx/imx8/Kconfig
+++ b/arch/arm/mach-imx/imx8/Kconfig
@@ -5,6 +5,7 @@
 
 config IMX8QXP
 	select IMX8
+	select SUPPORT_SPL
 	bool
 
 config SYS_SOC