topic: Added support for the SAM3X/A variants

topic: Added support for the SAM3X/A variants

Atmel introduced 7 new Cortex-M3 processors on 2012-02-28
SAM3X4C - 256KB flash
SAM3X4E - 256KB flash
SAM3X8C - 512KB flash
SAM3X8E - 512KB flash
SAM3X8H (Only on dev-kit - not in production...) - 512KB flash
SAM3A4C - 256KB flash
SAM3A8C - 256KB flash

The SAM3X/A processors still suffer from the "6 waitstates needed
to program device" errata.

The CIDR address for the SAM3X/A processors are different from the
other SAM3 processors.  Unfortunately, the chip identification register
is not at a constant address across all of the SAM3 series'. As a
consequence, a simple heuristic is used to find where it's
at... If the contents at the first address is zero, then we know
that the second address is where the chip id register is.
We can deduce this because for those SAM's that have the chip id @ 0x400e0940,
the first address, 0x400e0740, is located in the memory map of the Power
Management Controller (PMC). Furthermore, the address is not used by the PMC.
So when read, the memory controller returns zero.

Another interesting change is the flash bank address for flash bank 1.
It is not fixed at 0x00100000 like the Sam3U.  Bank 1 of the at91sam3a/x
series starts at 0x00080000 + half the total flash size.  Thus for the 256KB
devices Bank 1 is located at 0x000A0000, and for the 512KB devices Bank 1 is
located at 0x000C0000.

The configuration files for the SAM3X/A processors will follow

Change-Id: I6c3a707c00e05d993a2ad1d5a423f23b37ffd553
Signed-off-by: Olivier Schonken <olivier.schonken@gmail.com>
Reviewed-on: http://openocd.zylin.com/505
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>