arch,sim-se: Handle syscall retry/suppression in the syscall desc.

Rather than make each ISA include boilerplate to ignore a
SyscallReturn's value when it's marked as suppressed or needing a retry,
put that code into the SyscallDesc::doSyscall method instead.

That has two benefits. First, it removes a decent amount of code
duplication which is nice from a maintenance perspective. Second, it
puts the SyscallDesc in charge of figuring out what to do once a system
call implementation finishes. That will let it schedule a retry of the
system call for instance, without worrying about what the ISA is doing
with the SyscallReturn behind its back.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-1123

Change-Id: I76760cba75fd23e6e3357f6169c0140bee3f01b6
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54204
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
9 files changed