jtag/drivers/kitprog: workaround serious firmware problem

jtag/drivers/kitprog: workaround serious firmware problem

Since commit 88f429ead019fd6df96ec15f0d897385f3cef0d0
5321: target/cortex_m: faster reading of all CPU registers
debugging with a kitprog adapter freezes at debug entry.

How to replicate:
 openocd -f interface/kitprog.cfg -f target/psoc4.cfg

Connect to telnet server.
Make sure the target is running:
 resume

Halt the target:
 halt

Without this patch OpenOCD freezes in kitprog_hid_command()
in library call hid_write().

Reduce the number of SWD transactions sent in one USB bulk write
as a workaround, simply use shorter buffer.
For details see the comment in src/jtag/drivers/kitprog.c

Change-Id: I0116894d5ebf1655f6011f0d35acdbbc178cd48c
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/7107
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>