regulator: qpnp-regulator: add support for low-noise LDO type regulators

Add support for QPNP PMIC low-noise (LN) LDO type regulators.
This type of regulator provides very clean and constant voltage
at low current.  LN LDOs are used to power oscillators and RF
buffers.

Change-Id: Ibda540899b93bbb750f554e728d118b635bdbc0f
Signed-off-by: David Collins <collinsd@codeaurora.org>