n64cart: convert bi_disk to bi_bdev->bd_disk fix build

n64cart: convert bi_disk to bi_bdev->bd_disk fix build

My kernel robot report below:

  drivers/block/n64cart.c: In function ‘n64cart_submit_bio’:
  drivers/block/n64cart.c:91:26: error: ‘struct bio’ has no member named ‘bi_disk’
     91 |  struct device *dev = bio->bi_disk->private_data;
        |                          ^~
    CC      drivers/slimbus/qcom-ctrl.o
    CC      drivers/auxdisplay/hd44780.o
    CC      drivers/watchdog/watchdog_core.o
    CC      drivers/nvme/host/fault_inject.o
    AR      drivers/accessibility/braille/built-in.a
  make[2]: *** [scripts/Makefile.build:288: drivers/block/n64cart.o] Error 1

Fixes: 15f21b295a4d ("block: store a block_device pointer in struct bio");
Reported-by: k2ci <kernel-bot@kylinos.cn>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220321071216.1549596-1-liu.yun@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>