Try opposite values from P999DW service manual.
See what the tegra SPI slave returns.
Figure out what's failing the transfer.
Minor changes.
Remove mode bit not selected in GB kernel
Try another set of GPIO values from GB.
Sigh.
Go back to values that triggered an IRQ.
Some pretty trivial changes rolled into one commit:
 - Get rid of the spi2spi stuff for now. I'm not using it, and it makes the code harder to read.
 - Set a value on MRDY on init, as the GB kernel does.
 - Init the work queues on all SPIs, as the GB kernel does.
A couple potential GB differences.
Forgot critical return.
Pretty sure these are wrong...
Some more debug printks. Haven't built to see results yet.