srd: jtag: Various bugfixes.

srd: jtag: Various bugfixes.

Most importantly, both TDI and TDO are sampled at the rising TCK edge,
and only upon transitions from SHIFT-DR to SHIFT-DR and SHIFT-IR to SHIFT-IR
are we to save the TDI/TDO values (if I understood this correcly).

Also, start out in RUN-TEST/IDLE state for now. This is useful if you
have JTAG dumps which start "in the middle" somewhere, not in the
TEST-LOGIC-RESET state. For full dumps, the JTAG software usually issues
five TMS=1 cycles to force the JTAG state machine into TEST-LOGIC-RESET
anyway, so this works fine too.