gfio: add graph axis unit change notification callbacks

This enables code that uses the graph functions to change the axis
titles on the fly to display unit information which matches how the
tick labels are shortened.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/tickmarks.h b/tickmarks.h
index ab817a7..a8c1bf9 100644
--- a/tickmarks.h
+++ b/tickmarks.h
@@ -6,6 +6,7 @@
 	char string[20];
 };
 
-int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm);
+int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm,
+			int *power_of_ten, int use_KMG_symbols);
 
 #endif