net_dma: simple removal

Per commit "77873803363c net_dma: mark broken" net_dma is no longer used
and there is no plan to fix it.

This is the mechanical removal of bits in CONFIG_NET_DMA ifdef guards.
Reverting the remainder of the net_dma induced changes is deferred to
subsequent patches.

Marked for stable due to Roman's report of a memory leak in
dma_pin_iovec_pages():

    https://lkml.org/lkml/2014/9/3/177

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: David Whipple <whipple@securedatainnovations.ch>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: <stable@vger.kernel.org>
Reported-by: Roman Gushchin <klamm@yandex-team.ru>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

include/linux/skbuff.h

@@ -28,7 +28,6 @@
 #include <linux/textsearch.h>
 #include <net/checksum.h>
 #include <linux/rcupdate.h>
-#include <linux/dmaengine.h>
 #include <linux/hrtimer.h>
 #include <linux/dma-mapping.h>
 #include <linux/netdev_features.h>
@@ -515,11 +514,8 @@ struct sk_buff {
 	/* 6/8 bit hole (depending on ndisc_nodetype presence) */
 	kmemcheck_bitfield_end(flags2);
 
-#if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL
-	union {
-		unsigned int	napi_id;
-		dma_cookie_t	dma_cookie;
-	};
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	unsigned int	napi_id;
 #endif
 #ifdef CONFIG_NETWORK_SECMARK
 	__u32			secmark;