sfc: move common rx code

The moved code deals with managing rx buffers and queues.
A tiny bit of refactoring was required in other files to stitch the
code together.

Signed-off-by: Alexandru-Mihai Maftei <amaftei@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef10.c

@@ -5,6 +5,7 @@
  */
 
 #include "net_driver.h"
+#include "rx_common.h"
 #include "ef10_regs.h"
 #include "io.h"
 #include "mcdi.h"