regulator: rpm-smd: Add support for set_load function

Add support for regulator LDO "set_load" function, which is used
to set the regulator mode based on the load set by the consumers.
Also, add "qcom,regulator-hw-type" device tree property to
differentiate the pmic-ldo types, as the MODE_CTL settings of
PMIC5 LDOs are different from PMIC4 LDOs. Add this property for
trinket and qcs405 regulators.

Change-Id: Ib1223d5f33b975bb0815563e02d19dabfbde3ef1
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>