Input: cyttsp - use devm_regulator_bulk_get_enable()

Input: cyttsp - use devm_regulator_bulk_get_enable()

The driver does not try to power down the rails at system suspend or
when touchscreen is not in use, but rather enables regulators at probe
time. Power savings are achieved by requesting the controller to enter
low power mode.

Switch to devm_regulator_bulk_get_enable() instead of separately
requesting regulators, enabling them, and installing a custom
devm-action to disable them on unbind/remove, which simplifies the
code.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/ZrAgj9rG6oVqfdoK@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>