Add missing riscv attributes

[jerryzj]

• Based on RISCV ELF psABI document: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/2092568f7896ceaa1ec0f02569b19eaa42cd51c9/riscv-elf.adoc?plain=1#L1174
• The test ELF file is generated by the latest released RISC-V GNU Toolchain: https://github.com/riscv-collab/riscv-gnu-toolchain/releases/tag/2024.04.12

Signed-off-by: Jerry Zhang Jian jerry.zhangjian@sifive.com