Add missing ASM_PFX for HookAfterStubHeaderEnd.

Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14922 6f19259b-4bc3-4df7-8a09-765794883524
Merge branch 'master' of https://github.com/tianocore/edk2