ANDROID: KVM: arm64: Add host support for the nVHE hyp tracing

Now the nVHE hypervisor can write into a ring buffer. Add some support
to start the tracing and stop it.

This comes with a simple userspace interface tracing_on and per-CPU:

  - trace.X: non-consuming read of the ring buffer.
  - trace_pipe.X: consuming read of the ring buffer.

The hypervisor support to declare and decode hyp events will be
introduced later.

Bug: 229972309
Change-Id: I803b1fae8aaa5920d24adc547a9b5cc1c83d77f1
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>