For a bunch of rails we really don't do anything with them in Linux.
These are things like modem voltage rails that the modem manages these
itself and core rails (like IO rails) that are setup to just
automagically do the right thing by the firmware.

Let's stop even listing those rails in our device tree.

The net result of this is that some of these rails might be able to go
down to a lower voltage or perhaps transition to LPM (low power mode)
sometimes.

Here's a list of what we're doing and why:

* L1A - only goes to SoC and doesn't seem associated with any
  particular peripheral. Kernel isn't doing anything with
  this. Removing from dts. NET IMPACT: rail might drop from 1.2V to
  1.178V and switch to LPM in some cases depending on firmware.
* L2A - only goes to SoC and doesn't seem associated with any
  particular peripheral. Kernel isn't doing anything with
  this. Removing from dts. NET IMPACT: rail might switch to LPM in
  some cases depending on firmware.
* L3A - only goes to SoC and doesn't seem associated with any
  particular peripheral. Kernel isn't doing anything with
  this. Removing from dts. NET IMPACT: rail might switch to LPM in
  some cases depending on firmware.
* L5A - seems to be totally unused as far as I can tell and doesn't
  even come off QSIP. Removing from dts.
* L6A - only goes to SoC and doesn't seem associated with any
  particular peripheral (I think?). Kernel isn't doing anything with
  this. Removing from dts. NET IMPACT: rail might switch to LPM in
  some cases depending on firmware.
* L16A - Looks like this is only used for internal RF stuff. Removing
  from dts. NET IMPACT: rail might switch to LPM in some cases
  depending on firmware.
* L1C - Just goes to WiFi / Bluetooth. Trust how IDP has this set and
  put this back at 1.616V min.
* L4C - This goes out to the eSIM among other places. This looks like
  it's intended to be for SIM card and modem manages. NET IMPACT:
  rail might switch to LPM in some cases depending on firmware.
* L5C - This goes to the physical SIM.  This looks like it's intended
  to be for SIM card and modem manages. NET IMPACT: rail might drop
  from 1.8V to 1.648V and switch to LPM in some cases depending on
  firmware.

NOTE: in general for anything which is supposed to be managed by Linux
I still left it all forced to HPM since I'm not 100% sure that all the
needed calls to regulator_set_load() are in place and HPM is safer.
Switching more things to LPM can happen in a future patch.

ALSO NOTE: Power measurements showed no measurable difference after
applying this patch, so perhaps it should be viewed more as a cleanup
than any power savings.
Reviewed-by: Alexandru M Stan <amstan@google.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20201207143255.1.Ib92ec35163682dec4b2fbb4bde0785cb6e6dde27@changeidSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>