tcl/target/ti_k3: Add support for system reset using powerAP

tcl/target/ti_k3: Add support for system reset using powerAP

TI K3 Debug systems have a Power Access Port (Power-AP) which allows
for functionality such as reset via debugger that using the SPREC
register. SoCs/Boards that do not have support for SRST or TRST can
make use of this to force a system reset via debug access.

Change-Id: Ic5f9cc7f7fba77b353b0c0b42d8afc02502251a0
Signed-off-by: Shivasharan Nagalikar <shivasharan.nagalikar@ti.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8769
Reviewed-by: Nishanth Menon <nm@ti.com>
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>