Fix docs for bitmap.h

Bug: 135133301
Test: Generate docs

- Fix errors in bitmap documentation.
- Add links where relevant.
- Move comment in sensor.h so it will apply to the module, and not
AHardwareBuffer.

Change-Id: Iec00725522e74eccab9346665562081211a870eb
diff --git a/include/android/sensor.h b/include/android/sensor.h
index 12c00ad..e63ac4b 100644
--- a/include/android/sensor.h
+++ b/include/android/sensor.h
@@ -15,6 +15,9 @@
  */
 
 /**
+ * Structures and functions to receive and process sensor events in
+ * native code.
+ *
  * @addtogroup Sensor
  * @{
  */
@@ -42,12 +45,6 @@
  *   - DO NOT CHANGE THE LAYOUT OR SIZE OF STRUCTURES
  */
 
-/**
- * Structures and functions to receive and process sensor events in
- * native code.
- *
- */
-
 #include <android/looper.h>
 
 #include <stdbool.h>