Merge pull request #19 from skristiansson/for-openrisc

core additions
de0_nano: remove non-existing altera_virtual_jtag.v from src_files
wb_bfm: make Tp an external parameter and default to 0
wb_bfm: fix classic cycle accesses

Use the next task, common with burst accesses, instead of the
non-functional wait_for_ack task to wait for acks.
Also, completely remove the non-functional wait_for_ack task.