vk: precalculate gamma table early at startup

This is likely no the right way to do this. Address this when focusing on correct gamma overall for traditional renderer. Currently this is here just to make it have some non-zero values early.

engine/platform/sdl/vid_sdl.c

@@ -861,7 +861,11 @@ qboolean VID_CreateWindow( int width, int height, window_mode_t window_mode )
 
 		if( !GL_UpdateContext( ))
 		return false;
-
+	}
+	else if( glw_state.context_type == REF_VULKAN )
+	{
+		// FIXME this is probably not correct place or way to do it, just copypasting GL stuff
+		VID_StartupGamma();
 	}
 
 #else // SDL_VERSION_ATLEAST( 2, 0, 0 )