MdeModulePkg/PciBus: Simplify an complex if statement to pass VS2015

MdeModulePkg/PciBus: Simplify an complex if statement to pass VS2015

The logic in an if statement in PciIo is too complex and hard to understand
and make VS2015 build failure. The fix simplifies the logic.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18109 6f19259b-4bc3-4df7-8a09-765794883524