target/riscv: Remove redundant declaration pragmas

target/riscv: Remove redundant declaration pragmas

These are now generated by decodetree itself.

Tested-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Acked-by: Palmer Dabbelt <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>