blk_iocost: make read-only static array vrate_adj_pct const

The static array vrate_adj_pct is read-only, so make it const as
well.
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240911214124.197403-1-colin.i.king@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-iocost.c

@@ -648,7 +648,7 @@ static const struct ioc_params autop[] = {
  * vrate adjust percentages indexed by ioc->busy_level.  We adjust up on
  * vtime credit shortage and down on device saturation.
  */
-static u32 vrate_adj_pct[] =
+static const u32 vrate_adj_pct[] =
 	{ 0, 0, 0, 0,
 	  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
 	  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,