Fix compiler warnings in libpixelflinger

Change-Id: I6a5708ae6bc934b196d59d81a6cd550b05ed704f
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>
diff --git a/libpixelflinger/pixelflinger.cpp b/libpixelflinger/pixelflinger.cpp
index 84e584e..ea5bc8e 100644
--- a/libpixelflinger/pixelflinger.cpp
+++ b/libpixelflinger/pixelflinger.cpp
@@ -662,7 +662,7 @@
     }
 }
 
-void ggl_enable_stencil_test(context_t* c, int enable)
+void ggl_enable_stencil_test(context_t* /*c*/, int /*enable*/)
 {
 }