I'm curious, do you ever try using a search engine like Google before posting questions!? I'd say that the answers to 99.99% of the questions you ask have already been asked and answered before or in some cases is already sitting right in front of you... Case in point, while you've booted to the EFI Firmware have you even bothered to walk through all of the menu items!? Obviously not, because if you had you'd know that under the Boot Maintenance Manager there is Configure screen size. Also changing the screen size is not really necessary because you can do just like you can in many other Shells/Terminals and use the Shift + Page Up (or Shift + Up Arrow) and Shift + Page Down (or Shift + Down Arrow) or other modifier key combos to move up and down in the output buffer.
In many Shells/Terminals there are ways to prevent scrolling however the unsupported EFI Internal Shell does not have the typical *nix type commands (like less, more, head and tail) to pipe output through and hence you may need to scroll the output buffer to read it all! 
