sfc: Consistently test DEBUG macro, not EFX_ENABLE_DEBUG

The netif_dbg() macro is defined in <linux/netdevice.h>.  If the DEBUG
macro is defined, it logs a message at 'debug' level, otherwise it
does nothing.

In net_driver.h we define DEBUG if EFX_ENABLE_DEBUG is defined, but
this is too late for those source files that already got a
definition of netif_dbg() by including <linux/netdevice.h>

Get rid of EFX_ENABLE_DEBUG, and only define and test DEBUG.

In mtd.c, we do not use DEBUG as a condition flag but are forced to
use the DEBUG macro-function from <linux/mtd/mtd.h>.  Undefine DEBUG
before including it.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/mtd.c

@@ -10,6 +10,7 @@
 
 #include <linux/bitops.h>
 #include <linux/module.h>
+#undef DEBUG /* <linux/mtd/mtd.h> has its own use for DEBUG */
 #include <linux/mtd/mtd.h>
 #include <linux/delay.h>
 #include <linux/slab.h>

drivers/net/ethernet/sfc/net_driver.h

@@ -13,10 +13,6 @@
 #ifndef EFX_NET_DRIVER_H
 #define EFX_NET_DRIVER_H
 
-#if defined(EFX_ENABLE_DEBUG) && !defined(DEBUG)
-#define DEBUG
-#endif
-
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
@@ -42,7 +38,7 @@
 
 #define EFX_DRIVER_VERSION	"3.1"
 
-#ifdef EFX_ENABLE_DEBUG
+#ifdef DEBUG
 #define EFX_BUG_ON_PARANOID(x) BUG_ON(x)
 #define EFX_WARN_ON_PARANOID(x) WARN_ON(x)
 #else

drivers/net/ethernet/sfc/nic.c

@@ -801,7 +801,7 @@ static void efx_handle_rx_not_ok(struct efx_rx_queue *rx_queue,
 	 * error message.  FRM_TRUNC indicates RXDP dropped the packet due
 	 * to a FIFO overflow.
 	 */
-#ifdef EFX_ENABLE_DEBUG
+#ifdef DEBUG
 	if (rx_ev_other_err && net_ratelimit()) {
 		netif_dbg(efx, rx_err, efx->net_dev,
 			  " RX queue %d unexpected RX event "

drivers/net/ethernet/sfc/selftest.c

@@ -315,7 +315,7 @@ void efx_loopback_rx_packet(struct efx_nic *efx,
 	return;
 
  err:
-#ifdef EFX_ENABLE_DEBUG
+#ifdef DEBUG
 	if (atomic_read(&state->rx_bad) == 0) {
 		netif_err(efx, drv, efx->net_dev, "received packet:\n");
 		print_hex_dump(KERN_ERR, "", DUMP_PREFIX_OFFSET, 0x10, 1,