axihp_reader cleanup and version bump

 - removed sgn_data_enable (unused)
 - removed DELAY_WRITE_ENABLE_PROC (commented out)

Tested on real hardware, unchanged behaviour.
axihp_slave cleanup, address fix and version bump

 - whitespace cleanup in various places
 - byte order change in data_at()
 - use addr_next() in write_proc()
another round of whitespace cleanup