platform/x86: Use device_show_string() helper for sysfs attributes

platform/x86: Use device_show_string() helper for sysfs attributes

Deduplicate sysfs ->show() callbacks which expose a string at a static
memory location.  Use the newly introduced device_show_string() helper
in the driver core instead by declaring those sysfs attributes with
DEVICE_STRING_ATTR_RO().

No functional change intended.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/3ae8c9a73fbb291c1c863777af175c657a2a10e9.1713608122.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>