1. Update IoRead to support UINT64 also.

1. Update IoRead to support UINT64 also.
2. To be consistent, update PciCfgRead to support full S3BootScriptWidth(Uint8, FifoUint8 and FullUint8) like PciCfgWrite.
3. Use BuildLoopData() to get the addressStride and BufferStride to do PCI CFG operations.
4. Correct, refine and enhance some comments and debug messages.

Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13987 6f19259b-4bc3-4df7-8a09-765794883524