RISC-V: Fix abort when displaying data and partial instructions

If data is encountered that is not a power of two, dump all of the data with
a .<N>byte directive.  The current largest support risc-v instruction length
is 22, so the data over 22 bytes will be displayed by,
.insn, 22, ... + .<N-22>byte.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>