FWU: Add platform hook support for fwu metata

FWU: Add platform hook support for fwu metata

FWU metadata information is unavailable for platform-specific
operations since FWU initialization has not yet occurred.
The initialization function is invoked as part of the main
loop event. To address this, the FWU platform hook function
is introduced during FWU initialization, allowing metadata
processing with platform-specific operations.

Signed-off-by: Padmarao Begari <padmarao.begari@amd.com>
Link: https://lore.kernel.org/r/20250912100539.4127378-2-padmarao.begari@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>