Silicon/SynQuacer/Fip006Dxe: use proper accessor for unaligned access

This code may execute in SMM context, where unaligned accesses are
not permitted. So use ReadUnaligned32() instead of performing a
direct UINT32* cast.

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