isci: merge phy substates

Merged states and substates into one state machine, as we always
unconditionally transitioned to the substate machine it was straightforward to
enter that substate from the starting state.

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Adam Gruchala <adam.gruchala@intel.com>
[fixed construction, starting_state_enter, and starting check]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>