OvmfPkg/VirtioFsDxe: call IsTimeValid() before EfiTimeToEpoch()

OvmfPkg/VirtioFsDxe: call IsTimeValid() before EfiTimeToEpoch()

EmbeddedPkg/TimeBaseLib provides a verification function called
IsTimeValid(), for enforcing the UEFI spec requirements on an EFI_TIME
object.

When EFI_FILE_PROTOCOL.SetInfo() is called in order to update the
timestamps on the file, let's invoke IsTimeValid() first, before passing
the new EFI_FILE_INFO.{CreateTime,LastAccessTime,ModificationTime} values
to EfiTimeToEpoch().

This patch is not expected to make a practical difference, but it's better
to ascertain the preconditions of EfiTimeToEpoch() on the
EFI_FILE_PROTOCOL.SetInfo() caller. The FAT driver (EnhancedFatDxe) has a
similar check, namely in FatSetFileInfo() -> FatIsValidTime().

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20210107095051.22715-1-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>