[PATCH 2_4] Use config.h, not xparameters.h, for xilinx targets

[PATCH 2_4] Use config.h, not xparameters.h, for xilinx targets

Change the xilinx device drivers and board code to include config.h
instead of xparameters.h directly.  config.h always includes the
correct xparameters file.  This change reduces the posibility of
including the wrong file when adding a new xilinx board port

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>