staging: comedi: comedi.h: Fix comment for struct comedi_krange

The kernel-doc comment for `struct comedi_krange` refers to the macro
constant `RF_external`.  It should be `RF_EXTERNAL`, so fix it.  It also
documents the value of the constant as `(1 << 8)`, but the macro now
expands to the hexadecimal constant `0x100`, so use that as the
documented value.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi.h

@@ -667,7 +667,7 @@ struct comedi_rangeinfo {
  * by 1e6, so a @max value of %1000000 (with %UNIT_volt) represents a maximal
  * value of 1 volt.
  *
- * The only defined flag value is %RF_external (%1 << %8), indicating that the
+ * The only defined flag value is %RF_EXTERNAL (%0x100), indicating that the
  * the range needs to be multiplied by an external reference.
  */
 struct comedi_krange {