target/mips: Legalize Loongson insn flags

target/mips: Legalize Loongson insn flags

To match the actual status of Loongson insn, we split flags
for LMMI and LEXT from INSN_LOONGSON2F.

As Loongson-2F only implemented interger part of LEXT, we'll
not enable LEXT for the processor, but instead we're still using
INSN_LOONGSON2F as switch flag of these instructions.

All multimedia instructions have been moved to LMMI flag. Loongson-2F
and Loongson-3A are sharing these instructions.

Signed-off-by: Jiaxun Yang <[email protected]>
Reviewed-by: Aleksandar Markovic <[email protected]>
Signed-off-by: Aleksandar Markovic <[email protected]>
Message-Id: <20200614080049[email protected]>