OvmfPkg/IoMmuDxe: clean up used library classes

OvmfPkg/IoMmuDxe: clean up used library classes

The following library classes are not used by this module, so remove them
from the INF file's [LibraryClasses] section:
- DxeServicesTableLib
- UefiLib

The following library classes are used by this module, so add them to the
INF file's [LibraryClasses] section:
- BaseMemoryLib (e.g. via CopyMem())
- MemoryAllocationLib (e.g. via AllocatePool())

Sort the list of library classes (in both "IoMmuDxe.inf" and
"AmdSevIoMmu.h").

Remove all non-local #include directives from "IoMmuDxe.c"; both C files
of this module include "AmdSevIoMmu.h", and "AmdSevIoMmu.h" includes all
non-local headers already.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>