Fix compiler warnings in libpixelflinger

Change-Id: I6a5708ae6bc934b196d59d81a6cd550b05ed704f
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>
diff --git a/libpixelflinger/buffer.cpp b/libpixelflinger/buffer.cpp
index cbdab5a..dcb95c5 100644
--- a/libpixelflinger/buffer.cpp
+++ b/libpixelflinger/buffer.cpp
@@ -130,7 +130,7 @@
     }
 }
 
-void readRGB565(const surface_t* s, context_t* c,
+void readRGB565(const surface_t* s, context_t* /*c*/,
         uint32_t x, uint32_t y, pixel_t* pixel)
 {
     uint16_t v = *(reinterpret_cast<uint16_t*>(s->data) + (x + (s->stride * y)));
@@ -144,7 +144,7 @@
     pixel->s[3] = 5;
 }
 
-void readABGR8888(const surface_t* s, context_t* c,
+void readABGR8888(const surface_t* s, context_t* /*c*/,
         uint32_t x, uint32_t y, pixel_t* pixel)
 {
     uint32_t v = *(reinterpret_cast<uint32_t*>(s->data) + (x + (s->stride * y)));