ACPI: driver: Avoid using pnp.device_class for netlink handling

ACPI: driver: Avoid using pnp.device_class for netlink handling

Update several core ACPI device drivers that use
acpi_bus_generate_netlink_event() for generating netlink messages to
pass a string literal as its first argument instead of a pointer to
pnp.device_class in a given struct acpi_device, which will allow them
to avoid initializing the pnp.device_class field in the future.

The ACPI button driver that uses different acpi_device_class()
values for different button types will still pass it to
acpi_bus_generate_netlink_event(), but update it to use the
acpi_device_class() macro instead of open coding the pointer
access path.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/7944022.EvYhyI6sBW@rafael.j.wysocki