x86/sgx: Add missing xa_destroy() when virtual EPC is destroyed

xa_destroy() needs to be called to destroy a virtual EPC's page array
before calling kfree() to free the virtual EPC. Currently it is not
called so add the missing xa_destroy().

Fixes: 540745ddbc70 ("x86/sgx: Introduce virtual EPC for use by KVM guests")
Signed-off-by: Kai Huang <[e-mail]>
Signed-off-by: Borislav Petkov <[e-mail]>
Acked-by: Dave Hansen <[e-mail]>
Tested-by: Yang Zhong <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]

arch/x86/kernel/cpu/sgx/virt.c

···
 		list_splice_tail(&secs_pages, &zombie_secs_pages);
 	mutex_unlock(&zombie_secs_pages_lock);
 
+	xa_destroy(&vepc->page_array);
 	kfree(vepc);
 
 	return 0;