EmbeddedPkg: remove SiI3132 SATA controller driver
The SiI3132 SATA controller driver does not implement the UEFI driver
model, and is not a suitable example for new drivers to be based on.
Also, it is currently only used on a limited set of ARM development
platforms.
Due to this, it has been moved into the edk2-platforms repository,
alongside its remaining users, which have been updated to refer to it in
its new location. So drop this version from EmbeddedPkg.