target/riscv: Check for async flag in case of RISCV_EXCP_SEMIHOST.

RISCV_EXCP_SEMIHOST is set to 0x10, which can be a local interrupt id
as well. This change moves RISCV_EXCP_SEMIHOST to switch case so that
async flag check is performed before invoking semihosting logic.

Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231016111736.28721-3-rkanwal@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu_helper.c

@@ -1605,15 +1605,13 @@ void riscv_cpu_do_interrupt(CPUState *cs)
     target_ulong htval = 0;
     target_ulong mtval2 = 0;
 
-    if  (cause == RISCV_EXCP_SEMIHOST) {
-        do_common_semihosting(cs);
-        env->pc += 4;
-        return;
-    }
-
     if (!async) {
         /* set tval to badaddr for traps with address information */
         switch (cause) {
+        case RISCV_EXCP_SEMIHOST:
+            do_common_semihosting(cs);
+            env->pc += 4;
+            return;
         case RISCV_EXCP_LOAD_GUEST_ACCESS_FAULT:
         case RISCV_EXCP_STORE_GUEST_AMO_ACCESS_FAULT:
         case RISCV_EXCP_LOAD_ADDR_MIS: