ipmi sensor: fixd error reading ReadingCelsius

Signed-off-by: Joseph Liu <kwliu@nuvoton.com>
Signed-off-by: Tim Lee <timlee660101@gmail.com>
Change-Id: I4218f18a3d28310f4a5161e8a67cf8b98e40f98e
diff --git a/ipmi/test_ipmi_sensor.robot b/ipmi/test_ipmi_sensor.robot
index 12025ca..7973d6b 100644
--- a/ipmi/test_ipmi_sensor.robot
+++ b/ipmi/test_ipmi_sensor.robot
@@ -295,7 +295,7 @@
     @{redfish_readings}=  Redfish.Get Attribute  /redfish/v1/Chassis/chassis/Thermal  Temperatures
     FOR  ${data}  IN  @{redfish_readings}
         ${redfish_value}=  Set Variable If  '${data}[MemberId]' == '${member_id}'
-        ...  &{data}[ReadingCelsius]
+        ...  ${data}[ReadingCelsius]
         Exit For Loop If  '${data}[MemberId]' == '${member_id}'
     END
     [Return]  ${redfish_value}