ARM: Fix gen_nand probe structures contents

These three platforms didn't properly fill nr_chips in gen_nand 
registration and therefore depended on gen_nand bug fixed by commit 
81cbb0b1

 ("mtd: gen_nand: fix support for 
multiple chips")

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>