[MTD] NAND: Fix breakage all over the place

Following problems are addressed:

- wrong status caused early break out of nand_wait()
- removed the bogus status check in nand_wait() which
  is a relict of the abandoned support for interrupted
  erase.
- status check moved to the correct place in read_oob
- oob support for syndrom based ecc with strange layouts
- use given offset in the AUTOOOB based oob operations

Partially based on a patch from Vitaly Vool <vwool@ru.mvista.com>
Thanks to Savin Zlobec <savin@epico.si> for tracking down the
status problem.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>