erofs: fix wrong kunmap when using LZMA on HIGHMEM platforms

As the call trace shown, the root cause is kunmap incorrect pages:

 BUG: kernel NULL pointer dereference, address: 00000000
 CPU: 1 PID: 40 Comm: kworker/u5:0 Not tainted 6.2.0-rc5 #4
 Workqueue: erofs_worker z_erofs_decompressqueue_work
 EIP: z_erofs_lzma_decompress+0x34b/0x8ac
  z_erofs_decompress+0x12/0x14
  z_erofs_decompress_queue+0x7e7/0xb1c
  z_erofs_decompressqueue_work+0x32/0x60
  process_one_work+0x24b/0x4d8
  ? process_one_work+0x1a4/0x4d8
  worker_thread+0x14c/0x3fc
  kthread+0xe6/0x10c
  ? rescuer_thread+0x358/0x358
  ? kthread_complete_and_exit+0x18/0x18
  ret_from_fork+0x1c/0x28
 ---[ end trace 0000000000000000 ]---

The bug is trivial and should be fixed now.  It has no impact on
!HIGHMEM platforms.

Fixes: 622cead ("erofs: lzma compression support")
Cc: <[email protected]> # 5.16+
Reviewed-by: Yue Hu <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: hsiangkao

fs/erofs/decompressor_lzma.c

@@ -278,7 +278,7 @@ int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
 		}
 	}
 	if (no < nrpages_out && strm->buf.out)
-		kunmap(rq->in[no]);
+		kunmap(rq->out[no]);
 	if (ni < nrpages_in)
 		kunmap(rq->in[ni]);
 	/* 4. push back LZMA stream context to the global list */