system-arm: Fix FEAT_PAuth trapping in AArch64 bootloader
system-arm: Fix FEAT_PAuth trapping in AArch64 bootloader

Now that we start running the bootloader at EL3, we need to setup the
SCR_EL3 register so that it doesn't trap any pointer authentication
instruction.

This is fixing the booting process of Linux kernels making use of
FEAT_PAuth

Change-Id: I08aa96908dd2c16438448f3cc3c47a1271b2dfa8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61069
Reviewed-by: Richard Cooper <5451b9f082a6f419264dc2e8898d5200257ca9ce@arm.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Maintainer: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61736
Maintainer: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Reviewed-by: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Maintainer: Bobby Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>

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