ExitAirSensor: Fix off by 1 error

We were applying pwmPercent-- on success loop where
we shouldn't be.

Tested: Default fan setting was 100 in bios

Change-Id: Id5f0b139979db7f5fe570934a76d7f3ed56c2785
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/src/ExitAirTempSensor.cpp b/src/ExitAirTempSensor.cpp
index 6befd35..5e9fc29 100644
--- a/src/ExitAirTempSensor.cpp
+++ b/src/ExitAirTempSensor.cpp
@@ -327,8 +327,18 @@
         return pwmPercent;
     }
 
+    bool firstLoop = true;
     while (totalCFM > cfmMaxSetting)
     {
+        if (firstLoop)
+        {
+            firstLoop = false;
+        }
+        else
+        {
+            pwmPercent--;
+        }
+
         double ci = 0;
         if (pwmPercent == 0)
         {
@@ -355,12 +365,12 @@
         // divide by 100 since pwm is in percent
         totalCFM /= 100;
 
-        pwmPercent--;
         if (pwmPercent <= 0)
         {
             break;
         }
     }
+
     return pwmPercent;
 }