jtag: aspeed: pull TCK low to complete software clock cycle

- During CScript over ASD operations, an AWR reset triggered by host-error-monitor causes the system to hang at BIOS POST because TCK is left in the high state after aspeed_jtag_tck_cycle().
- Fix this by setting TCK to low at the end of aspeed_jtag_tck_cycle() to complete the clock cycle and maintain proper JTAG clock idling.

Reference for IPS number 01031704

Tested:
Verified that an AWR reset triggered by host-error-monitor no longer hangs at BIOS POST.

Change-Id: Icd6121b7c4b267a9a9f0e8440913d3de162cee96
Signed-off-by: Taly Tsai <taly.tsai@quanta.corp-partner.google.com>