hwmon: (dell-smm-hwmon) Mark functions as __init

i8k_get_dmi_data() and i8k_get_dell_signature() are
only called during module init and probe, which both
are marked as __init.
Also mark these function as __init to lower the runtime
memory footprint.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>
Tested-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20210728221557.8891-3-W_Armin@gmx.de


Signed-off-by: Guenter Roeck <linux@roeck-us.net>