KVM: arm64: Remove kvm_mmu_free_memory_caches()

kvm_mmu_free_memory_caches() is only called by kvm_arch_vcpu_destroy(),
so inline the implementation and get rid of the extra function.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20200911132529.19844-2-will@kernel.org