regulator: dbx500-prcmu: Remove unused fields from struct dbx500_regulator_info

The *dev is assigned but not used, remove it.
Current driver is using devm_regulator_register(), so no neeed to save
*rdev for clean up. Use a local variable instead.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>