Staging: SLICOSS: remove duplicated #include's

Removed duplicated #include's in drivers/staging/slicoss/slicoss.c.
  linux/delay.h
  linux/etherdevice.h
  linux/init.h
  linux/netdevice.h
  linux/pci.h
  linux/skbuff.h
  linux/slab.h
  linux/string.h

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>