perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv

Drop "support" for guest callbacks from architectures that don't implement
the guest callbacks.  Future patches will convert the callbacks to
static_call; rather than churn a bunch of arch code (that was presumably
copy+pasted from x86), remove it wholesale as it's useless and at best
wasting cycles.

A future patch will also add a Kconfig to force architcture to opt into
the callbacks to make it more difficult for uses "support" to sneak in in
the future.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-6-seanjc@google.com