ANDROID: KVM: arm64: Add header_page userspace descriptor for nVHE tracing

Added userspace file that describes the content of each hyp tracing
ring-buffer page. This follows the same format as the descriptor found
in the tracefs root to ensure compatibility with userspace trace tools.

Bug: 229972309
Change-Id: Ideebf37cb285b581c4cbe2a991a0df8c7ed61c0f
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>