[chip, testplan] Update SYSRST_CTL and ADC
[chip, testplan] Update SYSRST_CTL and ADC

- This commit addresses the comments and updates from the testplan
review meeting held on 6/07/2021.
- The meeting notes are below:
https://docs.google.com/document/d/1OhPP-HjciwKpIh0wWt1xqPqPf0Y0powmmww6xekwMeE/
- Updated SYSRST ctrl and ADC ctrl sections of the testplan

Signed-off-by: Srikrishna Iyer <2803d640feace36379942447842f26c7747b4dc3@google.com>

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