OpenGL: Enable filtering for EFB to Real XFB copies.

This fixes Real XFB Jaggies in OpenGL on games which use yscaling, such
as most PAL games.

This fixes the last of the "Real XFB Macroblocking" issues for opengl,
see issue #6503

Source/Core/VideoBackends/OGL/Src/TextureConverter.cpp

@@ -351,7 +351,10 @@ void EncodeToRamYUYV(GLuint srcTexture, const TargetRectangle& sourceRc, u8* des
 
 	s_rgbToYuyvProgram.Bind();
 
-	EncodeToRamUsingShader(srcTexture, sourceRc, destAddr, dstWidth / 2, dstHeight, 0, false, false);
+	// We enable linear filtering, because the gamecube does filtering in the vertical direction when
+	// yscale is enabled.
+	// Otherwise we get jaggies when a game uses yscaling (most PAL games)
+	EncodeToRamUsingShader(srcTexture, sourceRc, destAddr, dstWidth / 2, dstHeight, 0, false, true);
 	FramebufferManager::SetFramebuffer(0);
 	TextureCache::DisableStage(0);
 	g_renderer->RestoreAPIState();