hwmon: (pmbus/ir38064) Add driver for Infineon IR38064 Voltage Regulator

Add the pmbus driver for the Infineon ir38064 voltage regulator.

VOUT_MODE is not supported by the device.  The driver fakes linear16
mode with exponent value -8.

The device supports VOUT_PEAK, IOUT_PEAK, and TEMPERATURE_PEAK, however
this driver does not enable them.

Signed-off-by: Maxim Sloyko <maxims@google.com>
Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/ir38064

@@ -0,0 +1,64 @@
+Kernel driver ir38064
+=====================
+
+Supported chips:
+  * Infineon IR38064
+    Prefix: 'ir38064'
+    Addresses scanned: -
+    Datasheet: Publicly available at the Infineon webiste
+      https://www.infineon.com/dgdl/Infineon-IR38064MTRPBF-DS-v03_07-EN.pdf?fileId=5546d462584d1d4a0158db0d9efb67ca
+
+Datasheet is not publicly available.
+
+
+Authors:
+        Maxim Sloyko <maxims@google.com>
+        Patrick Venture <venture@google.com>
+
+Description
+-----------
+
+IR38064 is a Single-input Voltage, Synchronous Buck Regulator, DC-DC Converter.
+
+Usage Notes
+-----------
+
+This driver does not probe for PMBus devices. You will have to instantiate
+devices explicitly.
+
+Sysfs attributes
+----------------
+
+curr1_label		"iout1"
+curr1_input		Measured output current
+curr1_crit		Critical maximum current
+curr1_crit_alarm	Current critical high alarm
+curr1_max		Maximum current
+curr1_max_alarm	Current high alarm
+
+in1_label		"vin"
+in1_input		Measured input voltage
+in1_crit		Critical maximum input voltage
+in1_crit_alarm		Input voltage critical high alarm
+in1_min		Minimum input voltage
+in1_min_alarm		Input voltage low alarm
+
+in2_label		"vout1"
+in2_input		Measured output voltage
+in2_lcrit		Critical minimum output voltage
+in2_lcrit_alarm	Output voltage critical low alarm
+in2_crit		Critical maximum output voltage
+in2_crit_alarm		Output voltage critical high alarm
+in2_max		Maximum output voltage
+in2_max_alarm		Output voltage high alarm
+in2_min		Minimum output voltage
+in2_min_alarm		Output voltage low alarm
+
+power1_label		"pout1"
+power1_input		Measured output power
+
+temp1_input		Measured temperature
+temp1_crit		Critical high temperature
+temp1_crit_alarm	Chip temperature critical high alarm
+temp1_max		Maximum temperature
+temp1_max_alarm	Chip temperature high alarm