mtd: mxc_nand: configure pages per block for v2 controller

This patch initializes the pages per block field in CONFIG1 for
v2 controllers. It also sets the FP_INT field. This is the last
field not correctly initialized, so we can switch from
read/modify/write the CONFIG1 reg to just write the correct
value.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: John Ogness <john.ogness@linutronix.de>
Tested-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>