[ARM] 4192/1: AT91: Support for AT91SAM9XE processors.

Add support for the Atmel AT91SAM9XE range of processors.  These are
basically AT91SAM9260's with different amounts of internal SRAM and
Flash.

We make use of the existing AT91SAM9260 support, but just perform
run-time detection of the size of the internal SRAM.

Original patch from Nicolas Ferre.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>