fast_clock: Make fast_clock 130 MHz

In addition to making it 130 MHz, we also add a 26 MHz output to
fix some timing issues.
kovan-sd: Fix issues with 26 MHz clock

This takes advantage of the new 26 MHz output of the fast_clock
multiplier to improve routability.  It removes some timing errors
in synthesis.
nand_fifo: Rework buffer writer

Ultimately, this solves a problem where the wrong edge was getting
selected for NAND writing and reading.  This also improves logic,
removing a duplicate block.