Regulators: lp3971 - fail if platform data was not supplied

There is no point in completing probe if platform data is missing so
let's abort loading early.

Also, use kcalloc when allocating several instances of the same data
structure and mark setup_regulators() as __devinit since it is only
called from lp3971_i2c_probe() which is __devinit.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>