(Lakka) Fix init and reinit only textures

Before 30/05, the menu driver init was called only once on RA startup, now it is called after a window resize, or fullscreen switch, or after a rom is launched and the user trigger the menu. These changes fixed the texture bug in lakka, but also introduced some bugs due to the categories and item structures being reinited and the menu state contained it these structures was lost.

With this patch, we prevent the categories and items to be reinited again and again, only the textures are reinited. So the texture bug is now fixed. However the font cache textures are still white.

This patch also fix an hardcoded value in lakka_draw_icon.