regmap: adds missing braces in regmap_init()

It need to add curly braces because the inner for "if" has
two statements.

coccicheck says:
 drivers/base/regmap/regmap.c:765:2-44:
code aligned with following code on line 766

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>