wb_vic: change VAR reset value

For debugging purpose it is useful to have the reset value of this register different than 0x00000000. 0 can be a legit vector number for the first interrupt, so in case of trouble when the reset value is 0 we cannot be sure if this is the reset value or the first vector.

This reset value can be 0xFFFFFFFF or any random value 0xDEADBEEF