[dv/jtag] Fix two small jtag issue
[dv/jtag] Fix two small jtag issue

These PR fixes two small issues in jtag:
1. Add a clock cycle delay in between clock_en and drive_tms.
   This is to make sure the clock is stable before driving any signals.
2. Fix a port declaration from output to ref.

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@google.com>

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