efi_loader: support fmp versioning for multi bank update

This commit stores the firmware version into the array
of fmp_state structure to support the fmp versioning
for multi bank update. The index of the array is identified
by the bank index.

This modification keeps the backward compatibility with
the existing versioning feature.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>