hwmon: (adt7470) Fix some style issues

In preparation for the changes that follow fix up some existing style
issues.
Specifically:
- add blank line between variable declaration and code
- use strscpy instead of strlcpy
- remove unnecessary braces

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20210826024121.15665-2-chris.packham@alliedtelesis.co.nz
Signed-off-by: Guenter Roeck <linux@roeck-us.net>