libkern: Drop incorrect qsort optimization

See 5205b32de3 for details.

PR:		287089
MFC after:	1 week
Reviewed by:	jlduran
Differential Revision:	https://reviews.freebsd.org/D51919

sys/libkern/qsort.c

@@ -114,11 +114,10 @@ qsort(void *a, size_t n, size_t es, cmp_t *cmp)
 	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 	size_t d1, d2;
 	int cmp_result;
-	int swaptype_long, swaptype_int, swap_cnt;
+	int swaptype_long, swaptype_int;
 
 loop:	SWAPINIT(long, a, es);
 	SWAPINIT(int, a, es);
-	swap_cnt = 0;
 	if (n < 7) {
 		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 			for (pl = pm; 
@@ -147,7 +146,6 @@ loop:	SWAPINIT(long, a, es);
 	for (;;) {
 		while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
 			if (cmp_result == 0) {
-				swap_cnt = 1;
 				swap(pa, pb);
 				pa += es;
 			}
@@ -155,7 +153,6 @@ loop:	SWAPINIT(long, a, es);
 		}
 		while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
 			if (cmp_result == 0) {
-				swap_cnt = 1;
 				swap(pc, pd);
 				pd -= es;
 			}
@@ -164,18 +161,9 @@ loop:	SWAPINIT(long, a, es);
 		if (pb > pc)
 			break;
 		swap(pb, pc);
-		swap_cnt = 1;
 		pb += es;
 		pc -= es;
 	}
-	if (swap_cnt == 0) {  /* Switch to insertion sort */
-		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
-			for (pl = pm; 
-			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
-			     pl -= es)
-				swap(pl, pl - es);
-		return;
-	}
 
 	pn = (char *)a + n * es;
 	d1 = MIN(pa - (char *)a, pb - pa);