[chip testplan] Add JTAG test to access mem
[chip testplan] Add JTAG test to access mem

Add a testpoint to access memories in the chip over JTAG.

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

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