cpu: Use the built in << for VecReg and VecPredReg in ExeTrace.
cpu: Use the built in << for VecReg and VecPredReg in ExeTrace.

There's no reason to reimplement printing code when VecReg and
VecPredReg types already know how to print themselves.

Change-Id: I092c28143de286d765312122b81ce865a5184091
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42001
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Maintainer: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5