initial version taken from drivers/spi/spi-bcm2835.c
GIT-Commit: 2d6e75e894f355109d1f256cfdcfca9aafa90b9a
this is "upstream", so it should have full sign-offs
version that does work in principle with the raspbian kernel.
some changes mostly to get it working without device-tree
but already a bit of code for setting up the lines correctly...
to get filled in in bcm2835_spi_setup
renamed everything to dma to avoid name-space collissions
fixed CS issue when we have devices that have CS with reverse polarity
need to keep "account" of what the other devices on the bus have configured
The problem is that CS is sharing the setting for all 3 devices and we - so far - only take care of the one that is currently active
removed the spi-bcm2835 device and started from scratch based on the original spi-bcm2385.c that is already upstream in the kernel...