regulator: Get rid of lockdep warning

WARNING: at kernel/lockdep.c:2706 sysfs_add_file_mode+0x4c/0xa8()

Difference between v1 and v2:
Moved sysfs_attr_init() call as first one to access the structure.

Signed-off-by: Ameya Palande <ameya.palande@nokia.com>
CC: Liam Girdwood <lrg@slimlogic.co.uk>
CC: Mark Brown <broonie@opensource.wolfsonmicro.com>
CC: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>