Fixed the GLES2 shader count to be in sync with the enum

src/render/opengles2/SDL_shaders_gles2.h

@@ -45,11 +45,10 @@ typedef enum
     GLES2_SHADER_FRAGMENT_TEXTURE_NV21_JPEG,
     GLES2_SHADER_FRAGMENT_TEXTURE_NV21_BT601,
     GLES2_SHADER_FRAGMENT_TEXTURE_NV21_BT709,
-    GLES2_SHADER_FRAGMENT_TEXTURE_EXTERNAL_OES
+    GLES2_SHADER_FRAGMENT_TEXTURE_EXTERNAL_OES,
+    GLES2_SHADER_COUNT
 } GLES2_ShaderType;
 
-#define GLES2_SHADER_COUNT  16
-
 const Uint8 *GLES2_GetShader(GLES2_ShaderType type);
 
 #endif /* SDL_VIDEO_RENDER_OGL_ES2 */