mtd: teach mxc-nand about ONFI probing

this series implements support for ONFI probing in mxc-nand. Before a PARAM command was just ignored and the following read_bytes read whatever then happened to be available from the controller's RAM. But actually this wasn't that bad because the driver already failed to read the ONFI marker at offset 32 in response to the READID command and so the PARAM command wasn't issued at all :-)

Patch 1 is a robustness fix. Patch 2 is necessary to not make the controller stuck when the READPAGE command is issued before the flash chip is identified. Patch 3 is needed to be able to read more than 6 bytes in the read_byte callback. Finally patch 4 fixes the driver to allow reading out the READID ONFI marker and patch 5 implements support for the PARAM command.

Patch 6 implements a WARN that triggers when the core requests an unknown command from the driver. In the case of missing PARAM support it wouldn't have triggered because READID at offset 0x20 failed, too, but it might be worthwhile anyhow; I'm not sure though, so I marked it RFC. Not sure the set of commands will grow in the near future ...

Best regards
Uwe

Uwe Kleine-K?nig (6):
mtd: mxc-nand: Add a timeout when waiting for interrupt
mtd: mxc-nand: Only enable hardware checksumming for fully detected
flashes
mtd: mxc-nand: Do the word to byte mangling in the read_byte callback
mtd: mxc-nand: Allow to use column addresses different from 0
mtd: mxc-nand: Implement support for PARAM command
[RFC] mtd: mxc-nand: Warn on unimplemented commands