gianfar: Fix build with CONFIG_PM enabled

commit 4826857f

 ("gianfar: pass the
proper dev to DMA ops") introduced this build breakage:

  CC      drivers/net/gianfar.o
drivers/net/gianfar.c: In function 'gfar_suspend':
drivers/net/gianfar.c:552: error: 'struct gfar_private' has no member named 'dev'
drivers/net/gianfar.c: In function 'gfar_resume':
drivers/net/gianfar.c:601: error: 'struct gfar_private' has no member named 'dev'
make[2]: *** [drivers/net/gianfar.o] Error 1

Fix this by converting suspend and resume routines to use
gfar_private->ndev.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>