jtag/drivers: dmem: Add Emulated AP mode

jtag/drivers: dmem: Add Emulated AP mode

This emulation mode supports software translation of an AP request
into an address mapped transaction that does not rely on physical AP
hardware. This is necessary in some hardware such as K3 SoCs since the
hardware architecture anticipates a potential race condition between
AP doing direct memory access generating transactions back to system
bus and firewalls that data path out.

This emulation mode allows direct memory driver to emulate CoreSight
Access Port (AP) and reuse the SoC configuration meant for JTAG
debuggers.

Since the address ranges are flat in nature, the requisite memory base
and size will need to be provided a-priori to the driver for mapping.
The other design alternative would be to map requested memory map for
every register operation, but, that would defeat our intent of getting
max debug performance.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Jason Peck <jpeck@ti.com>
Change-Id: I2d3c5f7833f1973e90b4f6b247827f62fc2905d0
Reviewed-on: https://review.openocd.org/c/openocd/+/7089
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>