entropy-source: clarify access control, add opcode.

- Added opcode adjacent to ecall/ebreak.

- Added sseed/useed to mseccfg access control and updated table.

 On branch dev/next-release
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 Changes to be committed:
	modified:   doc/scalar/riscv-crypto-scalar-entropy-source.adoc
	modified:   extern/riscv-opcodes

 Changes not staged for commit:
	modified:   extern/riscv-gnu-toolchain (modified content)
	modified:   extern/sail-riscv (untracked content)