target: ls1088a: Add service processor

target: ls1088a: Add service processor

Normally the service processor is not necessary for debugging. However,
if you are using the hard-coded RCW or your boot source is otherwise
corrupt, then the general purpose processors will never be released from
hold-off. This will cause GDB to become confused if it tries to attach,
since they will appear to be running arm32 processors. To deal with
this, we can release the CPUs manually with the BRRL register. This
register cannot be written to from the axi target, so we need to do it
from the service processor target. This involves halting the service
processor, modifying the register, and then resuming it again. We try
and determine what state the service processor was in to avoid resuming
it if it was already halted.

The reset vector for the general purpose processors is determined by the
boot logation pointer registers in the device configuration unit.
Normally these are set using pre-boot initialization commands, but if
they are not set then they default to 0. This will cause the CPU to
almost immediately hit an illegal instruction. This is fine because we
will almost certainly want to attach to the processor and load a program
anyway.

I considered adding this as an event handler for either gdb-attach or
reset-init. However, this command shouldn't be necessary most of the
time, and so I don't think we should run it automatically.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Change-Id: I1b725292d8a11274d03af5313dc83678e10e944c
Reviewed-on: https://review.openocd.org/c/openocd/+/6850
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>