Use dynamic cas_ctl for each spi transfer
Use dynamic cas_ctl for each spi transfer

Rather than a single shared cas_ctl object with static buffers, put
a new cas_ctl object on the heap for every spi transfer. This removes
the need to lock shared resources. This also allows the IRQ handler
to call spi_transfer directly rather than using a workqueue.

Cascoda/ca8210-linux