mb/dell/optiplex_9020: Implement late HWM initialization

There are 4 different chassis types specified by vendor firmware, each
with a slightly different HWM configuration.

The chassis type to use is determined at runtime by reading a set of
4 PCH GPIOs: 70, 38, 17, and 1.

Additionally vendor firmware also provides an option to run the fans at
full speed. This is substituted with a coreboot nvram option in this
implementation.

This was tested to make fan control work on my OptiPlex 7020 SFF.

NOTE: This is superficially similar to the OptiPlex 9010's SCH5545
however the OptiPlex 9020's SCH5555 does not use externally
programmed EC firmware.

Change-Id: Ibdccd3fc7364e03e84ca606592928410624eed43
Signed-off-by: Mate Kukri <kukri.mate@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81529
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

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