cxl/mbox: Remove bad comment

__cxl_mem_mbox_send_cmd() no longer exists.  Remove the reference.
Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20211102202901.3675568-2-ira.weiny@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -148,8 +148,6 @@ static struct cxl_mem_command *cxl_mem_find_command(u16 opcode)
  * Mailbox commands may execute successfully yet the device itself reported an
  * error. While this distinction can be useful for commands from userspace, the
  * kernel will only be able to use results when both are successful.
- *
- * See __cxl_mem_mbox_send_cmd()
  */
 int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode, void *in,
 			  size_t in_size, void *out, size_t out_size)