drivers/cmsis-dap: update for newest protocol version

drivers/cmsis-dap: update for newest protocol version

The capabilities INFO command can now return two bytes, without this
patch, the capabilities would simply not be read and left as 0 (i.e. no
capabilities).

cf. https://arm-software.github.io/CMSIS_5/DAP/html/group__DAP__Info.html ;
https://github.com/ARM-software/CMSIS_5/blob/116866fd74756c88096e37cbd0066fadad583cad/CMSIS/DAP/Firmware/Source/DAP.c#L100-L111

Change-Id: Ibd894971edf1c120cae08089e5515ce5e9972323
Signed-off-by: PoroCYon <porocyon@titandemo.org>
Reviewed-on: http://openocd.zylin.com/6373
Tested-by: jenkins
Reviewed-by: Andrzej Sierżęga <asier70@gmail.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>