ArmVirtPkg: ArmCcaIoMmu: Provide an implementation for SetAttribute

The patch at "049695a0 MdeModulePkg/PciBusDxe: Add feedback
status for PciIoMap" adds support to propagate the error code
following the invocation of the IoMmu protocol SetAttribute()
operation.

Since the ArmCcaIoMmuDxe implementation of the SetAttribute()
function returned EFI_UNSUPPORTED, it resulted in the virtio
disk not being mounted.

Although there is nothing to be done in SetAttribute(), follow
the approach as done by the patch at "97c3f5b8  Provide an
implementation for SetAttribute" to validate the IoMmu access
method being requested against the IoMmu mapping operation and
return a suitable return code.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>