KVM: arm64: Fix meta-page unsharing in pKVM hyp tracing

KVM: arm64: Fix meta-page unsharing in pKVM hyp tracing

As the hyp_trace_buffer_unshare_hyp() function name suggests we should
unshare all the previously shared pages, otherwise we leak hyp-shared
pages which won't be reusable for hyp memory.

Fix the typo by calling __unshare_page() on the meta-page, ensuring all
previously shared pages are correctly unshared.

Fixes: 3aed038aac8d ("KVM: arm64: Add trace remote for the nVHE/pKVM hyp")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260521124613.911067-2-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>