Add basic uefi_variable_store implementation

Adds an implementation of the uefi_variable_store that forms
the backend for the smm_variable service provider. Orphan
variable index clean-up is not yet implemented.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I0924475a8819f488703065900d8efd01b48d42cf
5 files changed