tests: kernel: adopt new zephyr_count_bits util function

Adopt new zephyr_count_bits helper from util.h and avoid
having conflicting definition

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

Author: kartben

tests/kernel/common/src/bitarray.c

@@ -360,29 +360,13 @@ 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]);
+		popcnt += zephyr_count_bits(&ba->bundles[idx], sizeof(uint32_t));
 	}
 
 	return popcnt;