It's easier to implement mips16 shift instructions if we're not
examining the opcode inside gen_shift_{imm,}. So move ROTR and ROTRV
and do the special-case handling of SRL and SRLV inside decode_opc.
Likewise for their 64-bit counterparts.
Signed-off-by: Nathan Froyd <froydnj@codesourcery.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>