regulator: core: remove sysfs entry properly in regulator_put

With changes introduced by commit 222cc7b1 (regulator: core: Allow
multiple requests of a single supply mapping) on create_regulator,
regulator_put needs a corresponding update on sysfs entry removing.

Also regulator->dev still needs to get assigned in create_regulator,
otherwise, sysfs_remove_link call in regulator_put will get bypassed.

Reported-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>