Accoding the chapter 7.6 Trap Processing of the SPARC Architecture Manual v9,
the Trap Based Address Register is not modified as a trap is taken.

This fix allows booting FreeBSD-10.3-RELEASE-sparc64.

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>