SPARC: Emulation of GRLIB APB UART

This device exposes one parameter:
 - chardev (ptr) : Pointer to a qemu character device

Emulation of GrLib devices is base on the GRLIB IP Core User's Manual:
http://www.gaisler.com/products/grlib/grip.pdf

Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
