staging/iio: IIO_SIMPLE_DUMMY_BUFFER neds IIO_BUFFER

An obviously missing 'select' statement, without this we
get a link error

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: linux-iio@vger.kernel.org
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/Kconfig

@@ -36,10 +36,11 @@ config IIO_SIMPLE_DUMMY_EVENTS
          Add some dummy events to the simple dummy driver.
 
 config IIO_SIMPLE_DUMMY_BUFFER
-       boolean "Buffered capture support"
-       select IIO_KFIFO_BUF
-       help
-         Add buffered data capture to the simple dummy driver.
+	boolean "Buffered capture support"
+	select IIO_BUFFER
+	select IIO_KFIFO_BUF
+	help
+	  Add buffered data capture to the simple dummy driver.
 
 endif # IIO_SIMPLE_DUMMY