Update SmiManager() comments and implementation to follow the new rule clarified by PI 1.2.1 errata A. 
1. If at least one of the handlers returns EFI_WARN_INTERRUPT_SOURCE_QUIESCED or EFI_SUCCESS then the function will return EFI_SUCCESS.
   If a handler returns EFI_SUCCESS and HandlerType is not NULL then no additional handlers will be processed.
2. If a handler returns EFI_INTERRUPT_PENDING and HandlerType is not NULL then no additional handlers will be processed and EFI_INTERRUPT_PENDING will be returned.

Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>



git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14136 6f19259b-4bc3-4df7-8a09-765794883524