tcl/target: Unify Renesas R-Car JTAG reset config

tcl/target: Unify Renesas R-Car JTAG reset config

Both Gen2 and Gen3 used the same init_reset{} implementation,
pull it into common file and include it from both generations.
Moreover, this behavior is SoC specific, not board specific,
so move the common init_reset into target/ directory.

Change-Id: I5489a4bff9a786da8cb7fd7a515b0c9ce9dc16e3
Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Reviewed-on: http://openocd.zylin.com/5400
Tested-by: jenkins
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>