ARM: imx_v6_v7_defconfig: add CONFIG_FW_LOADER_USER_HELPER

To support loading sdma firmware automatically from rootfs, enable
CONFIG_FW_LOADER_USER_HELPER/CONFIG_FW_LOADER_USER_HELPER_FALLBACK.
Please get sdma firmware from below link and put it into
rootfs entry -- /lib/firmware/imx/sdma/:
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/imx/sdmaSigned-off-by: Robin Gong <yibin.gong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -90,6 +90,8 @@ CONFIG_RFKILL_INPUT=y
 CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_STANDALONE is not set
+CONFIG_FW_LOADER_USER_HELPER=y
+CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
 CONFIG_CMA_SIZE_MBYTES=64
 CONFIG_IMX_WEIM=y
 CONFIG_CONNECTOR=y