sim-se: Fixed initialization array size

Doubled the size of the zeroed auxiliary vector since 2 * intSize on
aarch64 > sizeof(uint64).

Change-Id: I5196b000a696e9ea3f2b5daa5d5bb071794369aa
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17088
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Maintainer: Brandon Potter <Brandon.Potter@amd.com>