stlink: skip rw-misc commands with TCP server

stlink: skip rw-misc commands with TCP server

The main purpose of TCP server is to allow multiple clients to
connect and share the same physical stlink.
The commands RW MISC don't lock the communication between command
and answer, thus cannot prevent another client to break this
sequence. The commands are not supposed to be used in shared mode.

Prevent the use of RW MISC commands on a (possibly) shared TCP
backend.
This degrades the overall performance, but the shared mode already
adds its own overhead, so this is not really an issue.

Change-Id: I713d912a269664859c8142932a9905d24b6d3caa
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6608
Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>