nvme-core: fix unsigned comparison warning in nvme_wait_freeze_timeout

nvme-core: fix unsigned comparison warning in nvme_wait_freeze_timeout

The timeout variable in nvme_wait_freeze_timeout() is an unsigned type.
Checking if it is <= 0 triggers a compiler warning because an unsigned
variable can never be negative.

Fix this warning by changing the type to long.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202605211257.STzj2Ujv-lkp@intel.com/
Fixes: 23b6d2cbf75f ("nvme: remove redundant timeout argument from nvme_wait_freeze_timeout")
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>