cxl: Fix compile warning for cxl_security_ops extern

Jonathan reported he has observed compiler warning when using running with
W=1 C=1 for cxl_security_ops that is declared as an extern in cxl/pmem.c.
Move to cxl.h to make it visible to all cxl sources.

Suggested-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Link: https://lore.kernel.org/linux-cxl/167771196186.3285982.18283746206612049722.stgit@djiang5-mobl3.local/
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

drivers/cxl/cxl.h

@@ -12,6 +12,8 @@
 #include <linux/node.h>
 #include <linux/io.h>
 
+extern const struct nvdimm_security_ops *cxl_security_ops;
+
 /**
  * DOC: cxl objects
  *

drivers/cxl/pmem.c

@@ -11,8 +11,6 @@
 #include "cxlmem.h"
 #include "cxl.h"
 
-extern const struct nvdimm_security_ops *cxl_security_ops;
-
 static __read_mostly DECLARE_BITMAP(exclusive_cmds, CXL_MEM_COMMAND_ID_MAX);
 
 static void clear_exclusive(void *mds)