hwmon: (pmbus/tps25990) Add initial support

hwmon: (pmbus/tps25990) Add initial support

Add initial support for the Texas Instruments TPS25990 eFuse.
This adds the basic PMBUS telemetry support for the device.

From Karol Przybylski:
  The tps25990_read_word_data function contains a block of unreachable code
  caused by the syntactic structure in the PMBUS_VIRT_READ_IIN_MAX case.

  Specifically, the return TPS25990_READ_IIN_PEAK; statement immediately
  exits the function, making the next lines unreachable.

  This patch removes the return statement, leaving the expected handling.
  Discovered in coverity: CID 1602227

Tested-by: Vaishnav Achath <vaishnav.a@ti.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
[groeck: Adjust to MODULE_IMPORT_NS API change]
[karprzy7@gmail.com: Fix unreachable code in tps25990_read_word_data]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>