target-tilegx: Use TILEGX_EXCP_OPCODE_UNKNOWN and TILEGX_EXCP_OPCODE_UNIMPLEMENTED...

target-tilegx: Use TILEGX_EXCP_OPCODE_UNKNOWN and TILEGX_EXCP_OPCODE_UNIMPLEMENTED correctly

For some cases, they are for TILEGX_EXCP_OPCODE_UNKNOWN, not for
TILEGX_EXCP_OPCODE_UNIMPLEMENTED.

Also for some cases, they are for TILEGX_EXCP_OPCODE_UNIMPLEMENTED, not
for TILEGX_EXCP_OPCODE_UNKNOWN.

When analyzing issues, the correct printing information is necessary,
e.g. grep UIMP in gcc testsuite output log for finding qemu tilegx
umimplementation issues, grep UNKNOWN for finding unknown instructions.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>