hwmon: (dell-smm) Use strscpy_pad()

Using strscpy_pad() allows for fewer memory accesses
since memset() will not unconditionally zero-out
the whole buffer.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Acked-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20211021190531.17379-3-W_Armin@gmx.de


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