CoffeelakeSiliconPkg: Remove SmmSpiFlashCommonLib

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3307



The library has been consolidated with instances in other Intel
silicon packages as a single instance in IntelSiliconPkg.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Sai Chaganty <rangasai.v.chaganty@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Sai Chaganty <rangasai.v.chaganty@intel.com>