tcl/board: Add STMicroelectronics STM32F7 Nucleo config

Tested with STM32F746ZG Nucleo development board.

Change-Id: Ia97b774b996a3be03e8e84342b93659c3632c18f
Signed-off-by: Marc Schink <openocd-dev@marcschink.de>
Reviewed-on: http://openocd.zylin.com/3516


Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

tcl/board/st_nucleo_f7.cfg

+# STMicroelectronics STM32F7 Nucleo development board
+# Known boards: NUCLEO-F746ZG and NUCLEO-F767ZI
+
+source [find interface/stlink-v2-1.cfg]
+
+transport select hla_swd
+
+source [find target/stm32f7x.cfg]
+
+reset_config srst_only