imx: Update FSL_MFGPROT config for iMX8M

Update the Kconfig and Makefile to allow build for iMX8M and
restrict the build only in u-boot.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Gaurav Jain <gaurav.jain@nxp.com>
diff --git a/arch/arm/mach-imx/Makefile b/arch/arm/mach-imx/Makefile
index 77e7270..aa0b644 100644
--- a/arch/arm/mach-imx/Makefile
+++ b/arch/arm/mach-imx/Makefile
@@ -38,8 +38,12 @@
 obj-y	+= cpu.o
 obj-$(CONFIG_SYS_I2C_MXC) += i2c-mxv7.o
 obj-$(CONFIG_ENV_IS_IN_MMC) += mmc_env.o
+endif
+ifeq ($(SOC),$(filter $(SOC),mx7 imx8m))
+ifneq ($(CONFIG_SPL_BUILD),y)
 obj-$(CONFIG_FSL_MFGPROT) += cmd_mfgprot.o
 endif
+endif
 ifeq ($(SOC),$(filter $(SOC),mx5 mx6 mx7))
 obj-$(CONFIG_IMX_VIDEO_SKIP) += video.o
 endif