Silicon/NorFlashSynQuacerLib: describe entire firmware region as FV

In order to allow for more flexibility when updating parts of the
firmware via capsule update, expand the description of the code FV
to cover the entire 4 MB region at the base of the NOR flash.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>