platform/x86: huawei-wmi: use sysfs_emit() instead of sprintf()

Follow the advice in Documentation/filesystems/sysfs.rst:
show() should only use sysfs_emit() or sysfs_emit_at() when formatting
the value to be returned to user space.

Signed-off-by: Ai Chao <aichao@kylinos.cn>
Link: https://lore.kernel.org/r/20240319064243.297320-1-aichao@kylinos.cn
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>