The nvme_user_cmd function was recently moved around from one file
to another, which made a warning reappear that I had fixed before
at some point:

drivers/nvme/host/core.c: In function 'nvme_user_cmd':
drivers/nvme/host/core.c:424:4: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]

This applies the same workaround that we have elsewhere in the
driver with an extra type cast to uintptr_t.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Fixes: 1673f1f0 ("nvme: move block_device_operations and ns/ctrl freeing to common code")
Link: https://lkml.org/lkml/2015/10/9/611Signed-off-by: NJens Axboe <axboe@fb.com>