fix(chip_if): Direct disconnect for ext_clk_rst
fix(chip_if): Direct disconnect for ext_clk_rst

vseq can only call `set_active()` function in `clk_rst_if.sv` at t=0.
This commit revises disconnect_all_interfaces() to avoid the fatal
error.

Signed-off-by: Eli Kim <3ca62a2ad87376be2697209a1770e1afdbbba220@opentitan.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan