Add some missing RISC-V ELF defines

[mhorne]

Summary

This adds defines for the RISC-V specific e_flags values, and some
missing static relocations.

The definitions come from the RISC-V ELF specification, found at:
https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md

[mhorne]

Include a definition for EF_RISCV_FLOAT_ABI_SOFT. Although this is not defined
in the RISC-V ELF spec, this zero value serves as an easy check.

[markj]

sys/sys/elf_common.h

373 ↗

(On Diff #59043)

I'm not sure it makes sense to include this one. If you wanted to test for the software ABI you'd write (e_flags & EF_RISCV_FLOAT_ABI_MASK) == 0, where the mask is 0x6.

[markj]

sys/sys/elf_common.h

373 ↗

(On Diff #59043)

After seeing the follow-up review, what you did here makes more sense. I'd just suggest adding a _MASK define instead of using _QUAD.

[mhorne]

Add EF_RISCV_FLOAT_ABI_MASK

[markj]

Approved.