arch-arm: Disable HVC when SCR_EL3.HCE is 0
arch-arm: Disable HVC when SCR_EL3.HCE is 0

This was already implemented for AArch32 but it had been wrongly
removed by:

https://gem5-review.googlesource.com/c/public/gem5/+/31394

Change-Id: Ida303d5ccb5d8568ca4e7faaedf9b4efd1cd88b5
Signed-off-by: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Reviewed-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32636
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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