Make sure that labeling is used consistently in all function headers.

include/sys/ioctl.h

@@ -110,7 +110,7 @@ extern "C"
  *   arg      The argument of the ioctl cmd, OR
  *   ...      A third argument of type unsigned long is still expected.
  *
- * Return:
+ * Returned Value:
  *   >=0 on success (positive non-zero values are cmd-specific)
  *   -1 on failure with errno set properly:
  *

include/sys/sendfile.h

@@ -87,7 +87,7 @@ extern "C"
  *   different semantics and prototypes.  sendfile() should not be used
  *   in portable programs.
  *
- * Input Parmeters:
+ * Input Parameters:
  *   infd   - A file (or socket) descriptor opened for reading
  *   outfd  - A descriptor opened for writing.
  *   offset - If 'offset' is not NULL, then it points to a variable

include/sys/time.h

@@ -160,7 +160,7 @@ extern "C"
  *   tv - The location to return the current time
  *   tz - Ignored
  *
- * Returned value:
+ * Returned Value:
  *   Zero (OK) on success;  -1 is returned on failure with the errno variable
  *   set appropriately.
  *
@@ -183,7 +183,7 @@ int gettimeofday(FAR struct timeval *tv, FAR struct timezone *tz);
  *   tv - The net to time to be set
  *   tz - Ignored
  *
- * Returned value:
+ * Returned Value:
  *   Zero (OK) on success;  -1 is returned on failure with the errno variable
  *   set appropriately.
  *