display: remove compiler warnings

Use correct typecasts and format specifiers and resolve
compiler warnings

Change-Id: I51b12ecb78a9a496cf1f76c3d32892a203f70c43
diff --git a/libcopybit/copybit_c2d.cpp b/libcopybit/copybit_c2d.cpp
index 7e2c500..d2b00dd 100644
--- a/libcopybit/copybit_c2d.cpp
+++ b/libcopybit/copybit_c2d.cpp
@@ -962,7 +962,7 @@
 /* Function to get the required size for a particular format, inorder for C2D to perform
  * the blit operation.
  */
-static size_t get_size(const bufferInfo& info)
+static int get_size(const bufferInfo& info)
 {
     int size = 0;
     int w = info.width;