target/riscv: Remove dead code after exception

We have already set DISAS_NORETURN in generate_exception,
which makes the exit_tb unreachable.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/riscv/insn_trans/trans_privileged.c.inc

@@ -22,8 +22,6 @@ static bool trans_ecall(DisasContext *ctx, arg_ecall *a)
 {
     /* always generates U-level ECALL, fixed in do_interrupt handler */
     generate_exception(ctx, RISCV_EXCP_U_ECALL);
-    exit_tb(ctx); /* no chaining */
-    ctx->base.is_jmp = DISAS_NORETURN;
     return true;
 }
 
@@ -65,8 +63,6 @@ static bool trans_ebreak(DisasContext *ctx, arg_ebreak *a)
     } else {
         generate_exception(ctx, RISCV_EXCP_BREAKPOINT);
     }
-    exit_tb(ctx); /* no chaining */
-    ctx->base.is_jmp = DISAS_NORETURN;
     return true;
 }