Adn even if it could allocate 2 GB it would still be your system RAM.
Even with DDR4-3200 you will sit with a bandwith of around 48 GB/s
As comparison a GTX 650 has around 80 GB/s, a GTX 750 Ti around 86 GB/s, a R7 260 has around 96 GB/s, the GTX 1050 and RX 460 have arond 112 GB/s, a RX 480 sits at 224 GB/s and a GTX 1080 has 320 GB/s
And even aside from your memory bandwitzh, the HD5500 performs around a R7 240 or GT 620. So unless you plan to play games from 2010 or older, you wouldn't have much fun with it anyways. And if that is your actual plan, there is no need for 2GB VMEM.