After

  faf01aef ("KVM: PPC: Merge powerpc's debugfs entry content into generic entry")

kvm_debugfs_dir is not used anywhere else outside of kvm_main.c

Unexport it and make it static.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240515150804.9354-1-bp@kernel.orgSigned-off-by: Sean Christopherson <seanjc@google.com>