tcl/board: Add Emcraft imx8 SOM BSB support

Tested with Olimex ARM-USB-TINY-H adapter

Simple commands work fine but there are currently issues when attaching
remote gdb or running virt2phys:

    https://sourceforge.net/p/openocd/tickets/201/

Change-Id: I86ccf1d93c5d23870bb522f92b3e2af190d529e8
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-on: http://openocd.zylin.com/4646
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

tcl/board/emcraft_imx8m-som-bsb.cfg

@@ -0,0 +1,22 @@
+#
+# configuration file for Emcraft IMX8M-SOM-BSB
+#
+
+# only JTAG supported
+transport select jtag
+
+# set a safe JTAG clock speed, can be overridden
+adapter_khz 1000
+
+# SRST and TRST are wired up
+reset_config trst_and_srst
+
+# delay after SRST goes inactive
+adapter_nsrst_delay 70
+
+# board has an i.MX8MQ with 4 Cortex-A53 cores
+set CHIPNAME imx8mq
+set CHIPCORES 4
+
+# source SoC configuration
+source [find target/imx8m.cfg]