Add the volatile keyword to NvmExpressDxe's Passthru CQ

Add the volatile keyword to NvmExpressDxe's Passthru CQ

This updates the relevant functions that expect a non-volatile
structure to be passed to them to take casts of the CQ
now that it is volatile.

Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Michael Kubacki <mikuback@linux.microsoft.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Signed-off-by: Oliver Smith-Denny <osde@linux.microsoft.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>
Acked-by: Michael Kubacki <michael.kubacki@microsoft.com>