EmbeddedPkg: Remove DXE_SAL_DRIVER

The DXE_SAL_DRIVER module type was introduced to support
Itanium (IPF) platforms. Since support for Itanium processors has been
dropped, the instances of DXE_SAL_DRIVER have been removed.

Ref: [3cb0a311cb7e747d7be5c5076d0fff76ad256d2b]

Cc: Sachin Ganesh <sachinganesh@ami.com>
Signed-off-by: Sathya Ravichandran <sathyar@ami.com>