Find physical address of userspace audio buffer
Created by: NilSet
Problem: Audio (through the AC '97 driver) was not being played.
Solution: Point the AC '97 bus master at the correct physical address of the audio buffer. Since this buffer is a userspace allocated Vec, it is necessary to get the context of the current process and search for the logical pointer in its pages.
TODOs: Handle the case where the buffer crosses a page boundary
Fixes: audio device reading the wrong memory
State: ready