drm/nouveau/core: get rid of math.h, replace log2i with order_base_2

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/core/engine/fifo/nvc0.c b/drivers/gpu/drm/nouveau/core/engine/fifo/nvc0.c
index 46dfa68..ce92f28 100644
--- a/drivers/gpu/drm/nouveau/core/engine/fifo/nvc0.c
+++ b/drivers/gpu/drm/nouveau/core/engine/fifo/nvc0.c
@@ -29,7 +29,6 @@
 #include <core/engctx.h>
 #include <core/event.h>
 #include <core/class.h>
-#include <core/math.h>
 #include <core/enum.h>
 
 #include <subdev/timer.h>
@@ -200,7 +199,7 @@
 
 	usermem = chan->base.chid * 0x1000;
 	ioffset = args->ioffset;
-	ilength = log2i(args->ilength / 8);
+	ilength = order_base_2(args->ilength / 8);
 
 	for (i = 0; i < 0x1000; i += 4)
 		nv_wo32(priv->user.mem, usermem + i, 0x00000000);