mtd/nand/bcm_umi: remove unused #include <linux/version.h>

Remove unused #include <linux/version.h>('s) in
  drivers/mtd/nand/bcm_umi_nand.c

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Acked-by: Leo Chen <leochen@broadcom.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>