Add MPS mp5990 hot-swap controller.

Change log:

v2 -> v3:
  - Support linear mode.
v1 -> v2:
  - Corrected dt-bindings description.
  - Added comments for Vout mode command.
  - Removed of_match_ptr()
v1:
  - Add support for MPS Multi-phase mp5990 Hot-Swap controller.

---
Peter Yin (2):
  dt-bindings: hwmon: Add mps mp5990 driver bindings
  hwmon: (pmbus) Add support for MPS Multi-phase mp5990

 .../devicetree/bindings/trivial-devices.yaml  |   2 +
 Documentation/hwmon/index.rst                 |   1 +
 Documentation/hwmon/mp5990.rst                |  84 +++++++++
 drivers/hwmon/pmbus/Kconfig                   |   9 +
 drivers/hwmon/pmbus/Makefile                  |   1 +
 drivers/hwmon/pmbus/mp5990.c                  | 177 ++++++++++++++++++
 6 files changed, 274 insertions(+)
 create mode 100644 Documentation/hwmon/mp5990.rst
 create mode 100644 drivers/hwmon/pmbus/mp5990.c

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2.25.1