Load and store UEFI variable index in chunks

Loading and storing such uefi variable index which is greater than
the RPC buffer, shall be done in chunks, which do not exceed the
RPC buffer size.
This way the number of UEFI variables is only limited by the
parameters of the non-volatile storage backend.

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Change-Id: Ie950ca4c307c478b2ac80bca8a237c26942419b3
3 files changed