stlink: detect mem_ap R/W and dequeue set TAR and CSW

stlink: detect mem_ap R/W and dequeue set TAR and CSW

By using the stlink commands for memory read write we can gain
some performance, but only when TAR and/or CSW are changed.
During long transfers with constant CSW and TAR auto-incremented
there is no gain, since the same amount of USB/TCP packet is used.
Plus, by dropping ADIv5 packed transfers the performance is lower
on 8 and 16 bits transfers.
This changes opens the opportunity for collapsing memory burst
accesses in a single stlink USB/TCP packet.

Initialize the values of enum queue_cmd to easily extract the word
size through a macro, even if this is not used here.

Change-Id: I6661a00d468a1591a253cba9feb3bdb3f7474f5a
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6603
Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>