Only apply fixed orientation letterbox ratio if orientation mismatch

The fixed orientation letterbox aspect ration should only be applied to
fixed orientation activity where their orientation does not match the
screen orientation.

Flag: EXEMPT bug fix
Test: atest WmTests:DesktopAppCompatAspectRatioPolicyTests,
      atest WmTests:DesktopModeLaunchParamsModifierTests
Fixes: 401322348

Change-Id: I135156ee167d42dbda92907f31c665db92e95892