MdeModulePkg/Xhci: Coding style update to follow EDKII C Coding Standards Spec.

Signed-off-by: Feng Tian <feng.tian@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14933 6f19259b-4bc3-4df7-8a09-765794883524
Fix comments format issue.

Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14934 6f19259b-4bc3-4df7-8a09-765794883524