mtd: nand: pxa3xx: Use 'length override' in ONFI paramater page read

The ONFI command 'parameter page read' needs a non-standard length.
Therefore, we enable the 'length override' field in NDCB0 and set
a non-zero 'length count' in NDCB3.

Additionally, the 'spare enable' bit must be disabled for any command
that sets a non-zero 'length count' in NDCB3.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>