x86/sgx: Correct kernel-doc's arg name in sgx_encl_release()

Fix the following kernel-doc warning:

  arch/x86/kernel/cpu/sgx/encl.c:392: warning: Function parameter \
    or member 'ref' not described in 'sgx_encl_release'

 [ bp: Massage commit message. ]
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210609035510.2083694-1-chenxiaosong2@huawei.com

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

@@ -383,7 +383,7 @@ const struct vm_operations_struct sgx_vm_ops = {
 
 /**
  * sgx_encl_release - Destroy an enclave instance
- * @kref:	address of a kref inside &sgx_encl
+ * @ref:	address of a kref inside &sgx_encl
  *
  * Used together with kref_put(). Frees all the resources associated with the
  * enclave and the instance itself.