Display the sUSD needed to fix C-Ratio

[0xclem]

Right now we've got this "Fix c-ratio" button in the Burn screen but it only uses the sUSD you have in your wallet.

It becomes an issue when you have no sUSD and/or other synths and you still want to know how much you should exchange/burn to fix your c-ratio.

So the idea is to have this info displayed somewhere in this screen.

[0xclem]

@bachstatter a quick win you should be able to do

[0xjocke]

👍