Introduce generic file interface

Signed-off-by: Boris Figovsky <borfig@gmail.com>
Add some values from BIOS Data Area

Signed-off-by: Boris Figovsky <borfig@gmail.com>
initial (and blocking) implementation of serial port

Signed-off-by: Boris Figovsky <borfig@gmail.com>
mem: add kernel virtual address to phisical address translation

Signed-off-by: Boris Figovsky <borfig@gmail.com>
pci: add pci command

Signed-off-by: Boris Figovsky <borfig@gmail.com>
file: add size

Signed-off-by: Boris Figovsky <borfig@gmail.com>