Corrected the pad constant connections to all be in the correct domain
(1.8V or 3.3V). Created a new "constant_block" module that generates
a single constant 1 and 0 value in the 1.8V domain, and used 7 of these
in the chip_io (and chip_io_alt) modules to create the 1.8V domain
constant signals for the seven pads belonging to the management (clock,
reset, flash SPI, and management GPIO).
Tim Edwards