Added tcl config scripts for SAM3A/X targets and devboard

Added tcl config scripts for SAM3A/X targets and devboard

The SAM3A/X processors that were released thus far is either
a SAM3A/X(4) - 256K, or a SAM3A/X(8) - 512K device.  Thus
the config files are per variant, and not per device.

Signed-off-by: Olivier Schonken <olivier.schonken@gmail.com>
Change-Id: I84d26d044e810eb428b1d6287907ea3bf8364c73
Signed-off-by: Olivier Schonken <olivier.schonken@gmail.com>
Reviewed-on: http://openocd.zylin.com/522
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>