ImpGraphic::ImplReadEmbedded: bSwap is false; remove dead code

Change-Id: Ie5b6b593e178d3752ebf7421af8aee4b50f75819
mbSwapUnderway always true inside ImpGraphic::ImplReadEmbedded

Change-Id: I641a9ca69d8e821f6b4e82ca98179a59b793345a