Cocoa: Silence warning on Big Endian host

__LITTLE_ENDIAN__ is undefined on Big Endian host.
Signed-off-by: NAndreas Färber <andreas.faerber@web.de>
Cc: John Arbuckle <programmingkidx@gmail.com>
Signed-off-by: Nmalc <av1474@comtv.ru>

cocoa.m

@@ -319,7 +319,7 @@ static int cocoa_keycode_to_qemu(int keycode)
             screen.bitsPerComponent, //bitsPerComponent
             screen.bitsPerPixel, //bitsPerPixel
             (screen.width * (screen.bitsPerComponent/2)), //bytesPerRow
-#if __LITTLE_ENDIAN__
+#ifdef __LITTLE_ENDIAN__
             CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB), //colorspace for OS X >= 10.4
             kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst,
 #else