Use register addresses from decode1 for dependency tracking

Use register addresses from decode1 for dependency tracking

This improves timing a little because the register addresses now come
directly from a latch instead of being calculated by
decode_input_reg_*.  The asserts that check that the two are the same
are now in decode2 rather than register_file.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>