uboot-imx

riscv: enable -fdata-sections

Enable the -fdata-sections compiler option for RISC-V. Buildman reports
the binary size decrease from this as 8365.3 bytes.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>