iwlwifi: Remove extern from function prototypes

There are a mix of function prototypes with and without extern
in the kernel sources.  Standardize on not using extern for
function prototypes.

Function prototypes don't need to be written with extern.
extern is assumed by the compiler.  Its use is as unnecessary as
using auto to declare automatic/local variables in a block.

Signed-off-by: Joe Perches <joe@perches.com>

drivers/net/wireless/iwlwifi/dvm/dev.h

@@ -270,7 +270,7 @@ struct iwl_sensitivity_ranges {
  * iwlXXXX_     <-- Hardware specific (implemented in iwl-XXXX.c for XXXX)
  *
  ****************************************************************************/
-extern void iwl_update_chain_flags(struct iwl_priv *priv);
+void iwl_update_chain_flags(struct iwl_priv *priv);
 extern const u8 iwl_bcast_addr[ETH_ALEN];
 
 #define IWL_OPERATION_MODE_AUTO     0