hwc2: Use floating value refresh rate

Matches corresponding changes in metadata on hwc1

Change-Id: I305a4d1f47cf3854f79456584ac013d15b57e9bc
CRs-Fixed: 1023652
diff --git a/sdm/libs/hwc2/hwc_layers.h b/sdm/libs/hwc2/hwc_layers.h
index b756c38..1026ff2 100644
--- a/sdm/libs/hwc2/hwc_layers.h
+++ b/sdm/libs/hwc2/hwc_layers.h
@@ -96,7 +96,7 @@
   DisplayError SetMetaData(const private_handle_t *pvt_handle, Layer *layer);
   DisplayError SetCSC(ColorSpace_t source, LayerCSC *target);
   DisplayError SetIGC(IGC_t source, LayerIGC *target);
-  uint32_t RoundToStandardFPS(uint32_t fps);
+  uint32_t RoundToStandardFPS(float fps);
 };
 
 struct SortLayersByZ {