tcl: add hi3798 target and Tocoding Poplar board config

tcl: add hi3798 target and Tocoding Poplar board config

This config covers the 4x Cortex A53 CPUs. A custom connector
is required from J14 to standard ARM JTAG on v1 boards. However
v2 hardware should have a standard FTSH-105-01-L-DV connector.

Pinmuxing code to enable JTAG pins is included in l-loader-poplar
repository, so board is flashed with open source code, JTAG
is available at very early boot. Alternatively the following
pokes can be issued from U-Boot to enable JTAG (e.g. to debug
hisilicon SDK).

mw 0xf8a210ec 0x130;
mw 0xf8a210f0 0x130;
mw 0xf8a210f4 0x130;
mw 0xf8a210f8 0x130;
mw 0xf8a210fc 0x130;
mw 0xf8a21100 0x130;

Change-Id: I2b83dfcb3dc5461c1620f94dd99aa7b31fdda59b
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-on: http://openocd.zylin.com/4161
Tested-by: jenkins
Reviewed-by: Jiri Kastner <cz172638@gmail.com>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>