Move all floats to doubles

The code was developed initially around a pid loop implemented using
floats.  Therefore, the code was converting back and forth between
double for sensor values as inputs and outputs from this PID loop.

Change-Id: I2d2919e1165103040729c9f16bb84fde3dd6b81b
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sysfs/sysfswrite.cpp b/sysfs/sysfswrite.cpp
index 1ea4c4d..6ca9b25 100644
--- a/sysfs/sysfswrite.cpp
+++ b/sysfs/sysfswrite.cpp
@@ -21,12 +21,12 @@
 
 void SysFsWritePercent::write(double value)
 {
-    float minimum = getMin();
-    float maximum = getMax();
+    double minimum = getMin();
+    double maximum = getMax();
 
-    float range = maximum - minimum;
-    float offset = range * value;
-    float ovalue = offset + minimum;
+    double range = maximum - minimum;
+    double offset = range * value;
+    double ovalue = offset + minimum;
 
     std::ofstream ofs;
     ofs.open(_writepath);