[ARM] 4354/1: AT91: Support ADS7846 touchsceen on SAM9263-EK board

Add support for the ADS7846 Touchscreen found on the Atmel
AT91SAM9263-EK board.

Signed-off-by: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>
Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>