i2c: mxs: do error checking and handling in PIO mode

In PIO mode we can end up with the same errors as in DMA mode, but as IRQs
are disabled there we have to check for them manually after each command.

Also don't use the big controller reset hammer when receiving a NAK from a
slave. It's sufficient to tell the controller to continue at a clean state.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>