RFC: Drop the adis16060 gyro driver from staging.

[Jonathan Cameron]

Hi All,

This part uses a strange double chip select which is really tricky to support
properly.  It could be done, but it's a lot of work to support one odd device.

Given the device is now 'not for new designs' I instead propose to simply
drop it from staging.

Does anyone mind / have the hardware to test if we try to add the support
nicely?

Thanks,

Jonathan