regulator: bd70528: drop struct bd70528

As a result of exporting the bd70528 specific locking functions
we no longer need struct bd70528. Remove references to
struct bd70528 from bd70528 regulator.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Mark Brown <broonie@kernel.org>