i386: firmware parsing and sev setup for -bios loaded firmware

i386: firmware parsing and sev setup for -bios loaded firmware

Don't register firmware as rom, not needed (see comment).
Add x86_firmware_configure() call for proper sev initialization.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220425135051.551037-4-kraxel@redhat.com>