KVM: arm64: Convert to the generic perf callbacks

Drop arm64's version of the callbacks in favor of the callbacks provided
by generic KVM, which are semantically identical.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211111020738.2512932-15-seanjc@google.com