Revert "mtd: mxc_nand: fix 2KiB pagesize NAND on i.MX27"

This reverts commit 71b7d0d90d536ae4e70929cc59a1a9f6ba457c6c.

The problem which that commit attempted to fix was a bootloader issue,
which had been misunderstood. The 'fix' causes lots of false bad blocks
for existing users with sane firmware.

Thanks to Mathieu Berland for diagnosing the problem coherently.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>