ArmVirtPkg: ArmPlatformDeviceInfoLib - add RTC parser

Add functionality to parse the Real Time Clock (RTC) info
from the FDT using the previously introduced generic device
parser and populate the PLATFORM_DEVICE_INFO structure.

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>