tcl/board: Add Renesas R-Car R8A7794 E2 Silk board

Add configuration for the Renesas R-Car R8A7794 E2
based Silk evaluation board.

Change-Id: I504b5630b1a2791ed6967c6c2af8851ceef9723f
Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
---
NOTE: This requires SW7[1] in position 1 (default is 0)
Reviewed-on: http://openocd.zylin.com/4532
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

tcl/board/renesas_silk.cfg

@@ -0,0 +1,16 @@
+# Renesas R-Car E2 Evaluation Board
+
+source [find target/renesas_r8a7794.cfg]
+
+reset_config trst_and_srst srst_nogate
+
+proc init_reset {mode} {
+    # Assert both resets: equivalent to a power-on reset
+    jtag_reset 1 1
+
+    # Deassert TRST to begin TAP communication
+    jtag_reset 0 1
+
+    # TAP should now be responsive, validate the scan-chain
+    jtag arp_init
+}