msm: rpm-regulator-smd: fix request suppression policy

The rpm-regulator-smd driver sends requests for a given regulator to
the RPM only if the regulator has been enabled by a Linux consumer.
If the regulator is disabled from Linux's point of view, then voltage
and current requests are buffered until the regulator is enabled again.
This buffering can lead to regulators being left at unnecessarily high
voltages when they are no longer needed.

Modify the request suppression policy so that current and voltage updates
are suppressed only before the first enable/disable request is sent for a
regulator or while the regulator is disabled if it has been marked as
apps-only. The first request sent for a given regulator must provide a
value for the enable/disable parameter otherwise the RPM will treat it as
an implicit disable request. This would break use-cases that require
certain regulators to be left on until sufficient software control is
initialized. Add a new device tree property, qcom,apps-only, which can be
used to specify that a given regulator supplies hardware that is fully
controlled by the applications processor.

CRs-Fixed: 533263
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>
Change-Id: I2a8820662e1471e5ff44f7d681d5d768da74980f