Fix linker warnings (errors on gcc) that resulted from r304510.

The variables that are extern in the netmap header file should be
defined in ixl_txrx.c (the file that is included in both ixl(4)/ixlv(4),
not in the main driver source files.

Reported by:	ed@, dim@, ngie@

sys/dev/ixl/if_ixlv.c

@@ -217,11 +217,6 @@ TUNABLE_INT("hw.ixlv.tx_itr", &ixlv_tx_itr);
 SYSCTL_INT(_hw_ixlv, OID_AUTO, tx_itr, CTLFLAG_RDTUN,
     &ixlv_tx_itr, 0, "TX Interrupt Rate");
 
-/* Fix when building as a standalone module when netmap is enabled */
-#if defined(DEV_NETMAP) && !defined(NETMAP_IXL_MAIN)
-int ixl_rx_miss, ixl_rx_miss_bufs, ixl_crcstrip;
-#endif
-        
 /*********************************************************************
  *  Device identification routine
  *

sys/dev/ixl/ixl_txrx.c

@@ -69,6 +69,7 @@ static inline u32 ixl_get_tx_head(struct ixl_queue *que);
 
 #ifdef DEV_NETMAP
 #include <dev/netmap/if_ixl_netmap.h>
+int ixl_rx_miss, ixl_rx_miss_bufs, ixl_crcstrip = 1;
 #endif /* DEV_NETMAP */
 
 /*

sys/dev/netmap/if_ixl_netmap.h

@@ -71,7 +71,6 @@ SYSCTL_DECL(_dev_netmap);
 /*
  * The xl driver by default strips CRCs and we do not override it.
  */
-int ixl_rx_miss, ixl_rx_miss_bufs, ixl_crcstrip = 1;
 #if 0
 SYSCTL_INT(_dev_netmap, OID_AUTO, ixl_crcstrip,
     CTLFLAG_RW, &ixl_crcstrip, 1, "strip CRC on rx frames");