performance_monitor: fix issue with freeing bitmap

Zephyr's bitarray had a problem when clearing the bit before freeing
it. Not clearing it changes nothing in overall logic so we can just not
do it.
Also fixes and issue with computing bitmap idx.

Signed-off-by: Tobiasz Dryjanski <tobiaszx.dryjanski@intel.com>

src/debug/telemetry/performance_monitor.c

@@ -145,12 +145,8 @@ struct perf_data_item_comp *perf_data_getnext(void)
 int perf_data_free(struct perf_data_item_comp * const item)
 {
 	/* find index of item */
-	int idx = (item - perf_data) / sizeof(*item);
-	int ret = perf_bitmap_clearbit(&performance_data_bitmap, idx);
-
-	if (ret < 0)
-		return ret;
-	ret = perf_bitmap_free(&performance_data_bitmap, idx);
+	int idx = (item - perf_data);
+	int ret = perf_bitmap_free(&performance_data_bitmap, idx);
 	if (ret < 0)
 		return ret;
 
@@ -473,10 +469,6 @@ int io_perf_monitor_release_slot(struct io_perf_data_item *item)
 	k_spin_unlock(&self->lock, key);
 
 	/* we assign data items ourselves so neither of those should ever fail */
-	ret = perf_bitmap_clearbit(&self->io_performance_data_bitmap, idx);
-	assert(!ret);
-	if (ret < 0)
-		return ret;
 	ret = perf_bitmap_free(&self->io_performance_data_bitmap, idx);
 	assert(!ret);
 	return ret;