imx: imx8_cpu: support i.MX9

Add CPU_IMX Kconfig
Support imx8_cpu driver for i.MX9

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/cpu/Makefile b/drivers/cpu/Makefile
index 3b38ba9..d4bbf6f 100644
--- a/drivers/cpu/Makefile
+++ b/drivers/cpu/Makefile
@@ -10,6 +10,7 @@
 obj-$(CONFIG_ARCH_IMX8) += imx8_cpu.o
 obj-$(CONFIG_ARCH_AT91) += at91_cpu.o
 obj-$(CONFIG_ARCH_MEDIATEK) += mtk_cpu.o
+obj-$(CONFIG_CPU_IMX) += imx8_cpu.o
 obj-$(CONFIG_CPU_MPC83XX) += mpc83xx_cpu.o
 obj-$(CONFIG_CPU_RISCV) += riscv_cpu.o
 obj-$(CONFIG_CPU_MICROBLAZE) += microblaze_cpu.o