blk-throttle: remove unused struct 'avg_latency_bucket'

'avg_latency_bucket' is unused since
commit bf20ab53 ("blk-throttle: remove
CONFIG_BLK_DEV_THROTTLING_LOW")

Remove it.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Link: https://lore.kernel.org/r/20240522172458.334173-1-linux@treblig.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-throttle.c

@@ -39,11 +39,6 @@ struct latency_bucket {
 	int samples;
 };
 
-struct avg_latency_bucket {
-	unsigned long latency; /* ns / 1024 */
-	bool valid;
-};
-
 struct throtl_data
 {
 	/* service tree for active throtl groups */