regulators: Convert to new SensorType enumeration

There are several types of voltage regulator sensors, such as vout,
iout, and temperature.

The sensor types were previously defined by the enumeration
pmbus_utils::SensorValueType.  This enumeration should not have been
placed in the pmbus_utils namespace because it is not specific to PMBus.

A new enumeration with the simpler name SensorType was created in
sensors.hpp in a previous commit.

Remove the old enumeration from pmbus_utils.  Convert affected files to
use the new enumeration.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: I4136b392b104edd3eee41ec29c779ad084c7c4de
diff --git a/phosphor-regulators/src/actions/pmbus_read_sensor_action.cpp b/phosphor-regulators/src/actions/pmbus_read_sensor_action.cpp
index fd58ae2..7ad0cad 100644
--- a/phosphor-regulators/src/actions/pmbus_read_sensor_action.cpp
+++ b/phosphor-regulators/src/actions/pmbus_read_sensor_action.cpp
@@ -74,7 +74,7 @@
 {
     std::ostringstream ss;
     ss << "pmbus_read_sensor: { ";
-    ss << "type: " << pmbus_utils::toString(type) << ", " << std::hex
+    ss << "type: " << sensors::toString(type) << ", " << std::hex
        << std::uppercase;
     ss << "command: 0x" << static_cast<uint16_t>(command) << ", " << std::dec
        << std::nouppercase;