uboot-imx

riscv: Remove setup.h

This was copied from ARM, and does not apply to RISC-V. While we
are here, bootm.h is eventually removed as its content is only
the inclusion of setup.h.

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