ArmVirtPkg: Add NULL instance of ArmCcaInitPeiLib

Add a NULL instance of ArmCcaInitPeiLib library that guest firmware
for VMMs that do not implement Arm CCA Realms can use.

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>