Fix compiler warnings in libpixelflinger

Change-Id: I6a5708ae6bc934b196d59d81a6cd550b05ed704f
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>
diff --git a/libpixelflinger/picker.cpp b/libpixelflinger/picker.cpp
index 030ef19..aa55229 100644
--- a/libpixelflinger/picker.cpp
+++ b/libpixelflinger/picker.cpp
@@ -26,7 +26,7 @@
 
 // ----------------------------------------------------------------------------
 
-void ggl_init_picker(context_t* c)
+void ggl_init_picker(context_t* /*c*/)
 {
 }