Silicon/Phytium: Add VariableFlashInfoLib

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3479



Add an instance for the library class VariableFlashInfoLib that
was recently introduced in MdeModulePkg. This allows the variable
driver to build successfully as it has a dependency on this
library class.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>