platform/x86: firmware_attributes_class: Simplify API

platform/x86: firmware_attributes_class: Simplify API

The module core already guarantees that a module can only be unloaded
after all other modules using its symbols have been unloaded.
As it's already the responsibility of the drivers using
firmware_attributes_class to clean up their devices before unloading,
the lifetime of the firmware_attributes_class can be bound to the
lifetime of the module.
This enables the direct usage of firmware_attributes_class from the
drivers, without having to go through the lifecycle functions,
leading to simplifications for both the subsystem and its users.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://lore.kernel.org/r/20250104-firmware-attributes-simplify-v1-2-949f9709e405@weissschuh.net
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>