yuzu/main: Fix host memory byte units. GB to GiB

I have `134850146304` bytes of ram and Yuzu was saying that I had `125.59 GB`
of ram. But `125.59` is actually the amount of gi**bi**bytes I have. In
gi**ga**bytes I would have `134.9`.

Additionally, I changed the `1024 / 1024 / 1024` here into the `_GiB`
user-literals that I added a while ago(#6519).

https://www.wolframalpha.com/input/?i=134850146304+bytes