nds32: deprecate it, together with aice adapter driver

nds32: deprecate it, together with aice adapter driver

The target nds32 and its companion adapter aice have not received
any real improvement since 2013.
It has been hard to keep them aligned during the evolution of
OpenOCD code, with no way for maintainers to really check if they
are still working.
No real documentation is present for them in OpenOCD.

The arch nds32 has been dropped from Linux kernel v5.18-rc1.

Deprecate both nds32 target and aice adapter with the target of
dropping them for v0.13.0.
Remove automatic build of aice, forcing user to select it.

Change-Id: Ib465d676246fa3b4e95c3d399ba9a5cf1f8b3baf
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6887
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Tested-by: jenkins