regulator: core: Release regulator-regulator supplies on error

If we fail while registering a regulator make sure we release the supply
for the regulator if there is one.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Cc: stable@vger.kernel.org