target-mips: Clean up switch fall through after commit fecd2646

Commit fecd2646 added a number of fall-throughs, but neglected to
properly document them as intentional.  Commit d9224450 cleaned that up
for many, but not all cases.  Take care of the remaining ones.

Spotted by Coverity.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

target-mips/translate.c

@@ -18729,6 +18729,7 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx)
     case OPC_SWL:
     case OPC_SWR:
         check_insn_opc_removed(ctx, ISA_MIPS32R6);
+        /* fall through */
     case OPC_SB ... OPC_SH:
     case OPC_SW:
          gen_st(ctx, op, rt, rs, imm);
@@ -18817,6 +18818,7 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx)
         case OPC_PS_FMT:
             check_cp1_enabled(ctx);
             check_insn_opc_removed(ctx, ISA_MIPS32R6);
+            /* fall through */
         case OPC_S_FMT:
         case OPC_D_FMT:
             check_cp1_enabled(ctx);
@@ -19000,6 +19002,7 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx)
     case OPC_LDL ... OPC_LDR:
     case OPC_LLD:
         check_insn_opc_removed(ctx, ISA_MIPS32R6);
+        /* fall through */
     case OPC_LWU:
     case OPC_LD:
         check_insn(ctx, ISA_MIPS3);
@@ -19008,6 +19011,7 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx)
         break;
     case OPC_SDL ... OPC_SDR:
         check_insn_opc_removed(ctx, ISA_MIPS32R6);
+        /* fall through */
     case OPC_SD:
         check_insn(ctx, ISA_MIPS3);
         check_mips_64(ctx);