target-mips: fix comments about SUB/DSUB

Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

target-mips/translate.c

@@ -1590,7 +1590,7 @@ static void gen_arith (CPUState *env, DisasContext *ctx, uint32_t opc,
             tcg_temp_free(t2);
             tcg_gen_brcondi_tl(TCG_COND_GE, t1, 0, l1);
             tcg_temp_free(t1);
-            /* operands of same sign, result different sign */
+	    /* operands of different sign, first operand and result different sign */
             generate_exception(ctx, EXCP_OVERFLOW);
             gen_set_label(l1);
             gen_store_gpr(t0, rd);
@@ -1665,7 +1665,7 @@ static void gen_arith (CPUState *env, DisasContext *ctx, uint32_t opc,
             tcg_temp_free(t2);
             tcg_gen_brcondi_tl(TCG_COND_GE, t1, 0, l1);
             tcg_temp_free(t1);
-            /* operands of same sign, result different sign */
+	    /* operands of different sign, first operand and result different sign */
             generate_exception(ctx, EXCP_OVERFLOW);
             gen_set_label(l1);
             gen_store_gpr(t0, rd);