Revert "mfd: syscon: Set name of regmap_config"

This reverts commit 500f9ff5.

The original commit is a duplication of the exactly previously added
commit 408d1d57

 ("mfd: syscon: Set regmap name to DT node name").
Revert the unnecessary later one.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>