accessing the usb device is still a hack,
but i do not want to rely on waveshares
'Generic Storage RamDisc 1.00' scsi inquiry "identifier".

pseudo_palette now properly translates colors to grayscale.
I though FB_VISUAL_STATIC_PSEUDOCOLOR and cmap were supposed
to do that but I did not get that to work. Keep cmap anyway,
because tools like fbi use it

mode 3-5 cause artefacts, when there are many adjacent updates,
such as during typing.

rendering less now terminates, console might be usable with this version

load image commands larger than something around 100kB cause the display to
freeze. 99880 bytes was fine, 102184 bytes were not.

i lost the history between this and the previous commit.

this version creates a working framebuffer device.
the framebuffer implementation needs optimisation, combining queued updates
as well as dropping updates that change nothing.

to late to split this into tidy commits, ups

removed everything from spidev.c which is not necessary to
hav eprobe called