mtd: gpmi: fix ECC regression

The "legacy" ECC layout used until 3.12-rc1 uses all the OOB area by
computing the ECC strength and ECC step size ourselves.

Commit 2febcdf8

 ("mtd: gpmi: set the BCHs geometry with the ecc info")
makes the driver use the ECC info (ECC strength and ECC step size)
provided by the MTD code, and creates a different NAND ECC layout
for the BCH, and use the new ECC layout. This causes a regression:

   We can not mount the ubifs which was created by the old NAND ECC layout.

This patch fixes this issue by reverting to the legacy ECC layout.

We will probably introduce a new device-tree property to indicate that
the new ECC layout can be used. For now though, for the imminent 3.12
release, we just unconditionally revert to the 3.11 behaviour.

This leaves a harmless cosmetic warning about an unused function. At
this point in the cycle I really don't care.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Huang Shijie <b32955@freescale.com>
Acked-by: Marek Vasut <marex@denx.de>
Tested-by: Marek Vasut <marex@denx.de>