staging: comedi: me4000: remove program_regbase from private data

The program_regbase variable in the private data is only used
when the board is first attached. This variable holds the pci
base address used to read/write the xilinx part to upload the
firmware.

Use a local variable in the xilinx_download() function to hold
this address and remove program_regbase from the private data.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>