hwmon: (core) remove redundant cast

struct attribute::name which this local variable name is eventually
assigned to is "const char*", and so is the template parameter. We might
as well preserve the constness all the way through.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>