tcg: Remove TCGOpDef.used

The last user of this field disappeared in f69d277ece.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/tcg/tcg.h

@@ -1015,9 +1015,6 @@ typedef struct TCGOpDef {
     uint8_t nb_oargs, nb_iargs, nb_cargs, nb_args;
     uint8_t flags;
     TCGArgConstraint *args_ct;
-#if defined(CONFIG_DEBUG_TCG)
-    int used;
-#endif
 } TCGOpDef;
 
 extern TCGOpDef tcg_op_defs[];