iio: imu: st_lsm6dsx: Simplify using devm_regulator_*get_enable()

iio: imu: st_lsm6dsx: Simplify using devm_regulator_*get_enable()

Use devm_regulator_bulk_get_enable() instead of open coded bulk-get,
bulk-enable, add-action-to-disable-at-detach - pattern.

A functional change (which seems like a bugfix) is that if
regulator_bulk_get fails, the enable is not attempted.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/876e58428cec056d51070e49eff559e2d7c23b12.1660934107.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>