fwu: add dependency checks for selecting FWU metadata version

fwu: add dependency checks for selecting FWU metadata version

The FWU code supports both versions of the FWU metadata, i.e. v1 and
v2. A platform can then select one of the two versions through a
config symbol. Put a dependency in the FWU metadata version selection
config symbol to ensure that both versions of the metadata cannot be
enabled.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Tested-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>