hps: increase system clock frequency to 64MHz
hps: increase system clock frequency to 64MHz

The tools can reliably make 64MHz now.

Signed-off-by: Dan Callaghan <c6268a61d01f53ee8e097a439feb27b30b61efda@google.com>

google/CFU-Playground,google/CFU-Playground,google/CFU-Playground,google/CFU-Playground