nvmes: set sensor value unit with DegreesC

Current Nvme temperature sensor unit is showed as Amperes.
Set temperature sensor value unit with DegreesC

Tested result:
root@bletchley:~# busctl get-property xyz.openbmc_project.nvme.manager /xyz/openbmc_project/sensors/temperature/nvme1 xyz.openbmc_project.Sensor.Value Unit
s "xyz.openbmc_project.Sensor.Value.Unit.DegreesC"

Signed-off-by: Potin Lai <potin.lai@quantatw.com>
Change-Id: I26e5f2629a6b9893346eb58aa41bfc211efb78d4
diff --git a/nvmes.hpp b/nvmes.hpp
index 61c027f..436dd38 100644
--- a/nvmes.hpp
+++ b/nvmes.hpp
@@ -40,6 +40,7 @@
     NvmeSSD(sdbusplus::bus::bus& bus, const char* objPath) :
         NvmeIfaces(bus, objPath), bus(bus)
     {
+        ValueIface::unit(Unit::DegreesC);
     }
 
     /** @brief Set sensor value temperature to nvme D-bus  */