Linux 5.3: Fix switch() fall though compiler errors

Fix some switch() fall-though compiler errors:

    abd.c:1504:9: error: this statement may fall through

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #9170

module/lua/llex.c

@@ -431,9 +431,12 @@ static int llex (LexState *ls, SemInfo *seminfo) {
         if (sep >= 0) {
           read_long_string(ls, seminfo, sep);
           return TK_STRING;
-        }
-        else if (sep == -1) return '[';
-        else lexerror(ls, "invalid long string delimiter", TK_STRING);
+        } else if (sep == -1) {
+		return '[';
+        } else {
+		lexerror(ls, "invalid long string delimiter", TK_STRING);
+		break;
+	}
       }
       case '=': {
         next(ls);

module/zfs/abd.c

@@ -1370,8 +1370,10 @@ abd_raidz_gen_iterate(abd_t **cabds, abd_t *dabd,
 		switch (parity) {
 			case 3:
 				len = MIN(caiters[2].iter_mapsize, len);
+				/* falls through */
 			case 2:
 				len = MIN(caiters[1].iter_mapsize, len);
+				/* falls through */
 			case 1:
 				len = MIN(caiters[0].iter_mapsize, len);
 		}
@@ -1461,9 +1463,11 @@ abd_raidz_rec_iterate(abd_t **cabds, abd_t **tabds,
 			case 3:
 				len = MIN(xiters[2].iter_mapsize, len);
 				len = MIN(citers[2].iter_mapsize, len);
+				/* falls through */
 			case 2:
 				len = MIN(xiters[1].iter_mapsize, len);
 				len = MIN(citers[1].iter_mapsize, len);
+				/* falls through */
 			case 1:
 				len = MIN(xiters[0].iter_mapsize, len);
 				len = MIN(citers[0].iter_mapsize, len);

module/zfs/vdev_raidz_math_scalar.c

@@ -142,6 +142,7 @@ static const struct {
 		a.b[6] = mul_lt[a.b[6]];				\
 		a.b[5] = mul_lt[a.b[5]];				\
 		a.b[4] = mul_lt[a.b[4]];				\
+		/* falls through */					\
 	case 4:								\
 		a.b[3] = mul_lt[a.b[3]];				\
 		a.b[2] = mul_lt[a.b[2]];				\