target/stm32h7x: add support of dual core variant of STM32H7

target/stm32h7x: add support of dual core variant of STM32H7

STM32H7x7 and STM32H7x5 devices contains two cores : CM7 + CM4
The second core creation is only done when
  * DUAL_CORE variable is set to true
  * non HLA interface is used

A second check for the second core existence is done in cpu1 examine-end
Once the second core is detected it gets examined.

Furthermore, the script provides a configurable CTI usage in order to halt
the cores simultaneously.

Tested on Rev X and V devices.

PS: the indentation was a mix of spaces and tabs, all changed to tabs.

Change-Id: Iad9c30826965ddb9be5dee628bc2e63f953bbcb8
Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: http://openocd.zylin.com/5130
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>