sim: mips: fix -Wimplicit-fallthrough warnings

Seems like these cases were meant to fallthru.

sim/mips/cp1.c

@@ -262,6 +262,7 @@ store_fpr (sim_cpu *cpu,
 	{
 	case fmt_uninterpreted_32:
 	  fmt = fmt_uninterpreted;
+	  ATTRIBUTE_FALLTHROUGH;
 	case fmt_single:
 	case fmt_word:
 	  if (STATE_VERBOSE_P (SD))
@@ -274,6 +275,7 @@ store_fpr (sim_cpu *cpu,
 
 	case fmt_uninterpreted_64:
 	  fmt = fmt_uninterpreted;
+	  ATTRIBUTE_FALLTHROUGH;
 	case fmt_uninterpreted:
 	case fmt_double:
 	case fmt_long:
@@ -294,6 +296,7 @@ store_fpr (sim_cpu *cpu,
 	{
 	case fmt_uninterpreted_32:
 	  fmt = fmt_uninterpreted;
+	  ATTRIBUTE_FALLTHROUGH;
 	case fmt_single:
 	case fmt_word:
 	  FGR[fpr] = (value & 0xFFFFFFFF);
@@ -302,6 +305,7 @@ store_fpr (sim_cpu *cpu,
 
 	case fmt_uninterpreted_64:
 	  fmt = fmt_uninterpreted;
+	  ATTRIBUTE_FALLTHROUGH;
 	case fmt_uninterpreted:
 	case fmt_double:
 	case fmt_long:

sim/mips/interp.c

@@ -1247,7 +1247,7 @@ sim_monitor (SIM_DESC sd,
 	if (A0 == 0)	/* waitflag == NOWAIT */
 	  V0 = (unsigned_word)-1;
       }
-     /* Drop through to case 11 */
+     ATTRIBUTE_FALLTHROUGH;
 
     case 11: /* char inbyte(void) */
       {
@@ -1904,6 +1904,7 @@ signal_exception (SIM_DESC sd,
 	 }
        /* else fall through to normal exception processing */
        sim_io_eprintf(sd,"ReservedInstruction at PC = 0x%s\n", pr_addr (cia));
+       ATTRIBUTE_FALLTHROUGH;
      }
 
     default:
@@ -2329,6 +2330,7 @@ decode_coproc (SIM_DESC sd,
 				  "Warning: PC 0x%lx:interp.c decode_coproc DEADC0DE\n",
 				  (unsigned long)cia);
 		GPR[rt] = 0xDEADC0DE; /* CPR[0,rd] */
+		ATTRIBUTE_FALLTHROUGH;
 		/* CPR[0,rd] = GPR[rt]; */
 	      default:
 		if (op == cp0_mfc0 || op == cp0_dmfc0)

sim/mips/m16e.igen

@@ -212,16 +212,22 @@
   switch (xsregs) {
   case 7:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[30]);
+    ATTRIBUTE_FALLTHROUGH;
   case 6:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[23]);
+    ATTRIBUTE_FALLTHROUGH;
   case 5:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[22]);
+    ATTRIBUTE_FALLTHROUGH;
   case 4:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[21]);
+    ATTRIBUTE_FALLTHROUGH;
   case 3:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[20]);
+    ATTRIBUTE_FALLTHROUGH;
   case 2:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[19]);
+    ATTRIBUTE_FALLTHROUGH;
   case 1:
     do_store (SD_,AccessLength_WORD, temp -= 4, 0, GPR[18]);
   }