nvme: Fixes u64 division which breaks i386 builds

Uses div_u64 for u64 division and round_down, a bitwise operation,
instead of rounddown, which uses a modulus.

Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
1 file changed