target/microblaze: Add the div-zero-exception property

target/microblaze: Add the div-zero-exception property

Add the div-zero-exception property to control if the core
traps divizions by zero.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Luc Michel <luc.michel@greensocs.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>