RISC-V Disassembler

RISC-V Disassembler

The RISC-V disassembler has no dependencies outside of the 'disas'
directory so it can be applied independently. The majority of the
disassembler is machine-generated from instruction set metadata:

- https://github.com/michaeljclark/riscv-meta

Expected checkpatch errors for consistency and brevity reasons:

ERROR: line over 90 characters
ERROR: trailing statements should be on next line
ERROR: space prohibited between function name and open parenthesis '('

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Michael Clark <mjc@sifive.com>