regmap: potentially duplicate the name string stored in regmap

Currently we just copy over the pointer passed to regmap_init() in
the regmap config struct. To be on the safe side: duplicate the string
with kstrdup_const() so that if an unaware user passes an address to
a stack-allocated buffer, we won't crash.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Mark Brown <broonie@kernel.org>