efifb dumbfb question

Hello,

I had a programming question. Is it possible to have a WSDISPLAYIO_MODE_DUMBFB
rendered on only one tty instead of having the mmap memory affecting every
tty despite the socket only targetting one.

For context, I'm writting a program that does rendering with efifb and when
trying to switch tty (with the shortcuts) the framebuffer that has been
mmaped carries over.

```Small snippet
fbuf = mmap(0, fbinfo.width * fbinfo.height * (fbinfo.depth / 8), PROT_WRITE |
PROT_READ, MAP_SHARED, sockfd, (off_t)0);

memset(fbuf, 255, fbinfo.width * fbinfo.height * (fbinfo.depth / 8));
```

Xavier