Revert "tests: kernel: adopt new count_bits util function"

This reverts commit e34270519e.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

tests/kernel/common/src/bitarray.c

@@ -355,13 +355,29 @@ void alloc_and_free_predefined(void)
 		     "sys_bitarray_alloc() failed bits comparison");
 }
 
+static inline size_t count_bits(uint32_t val)
+{
+	/* Implements Brian Kernighan’s Algorithm
+	 * to count bits.
+	 */
+
+	size_t cnt = 0;
+
+	while (val != 0) {
+		val = val & (val - 1);
+		cnt++;
+	}
+
+	return cnt;
+}
+
 size_t get_bitarray_popcnt(sys_bitarray_t *ba)
 {
 	size_t popcnt = 0;
 	unsigned int idx;
 
 	for (idx = 0; idx < ba->num_bundles; idx++) {
-		popcnt += count_bits(&ba->bundles[idx], sizeof(uint32_t));
+		popcnt += count_bits(ba->bundles[idx]);
 	}
 
 	return popcnt;