[ARM] 3956/1: AT91: Carmeva board update

This patch updates the Carmeva board support:
      * Specify the MMC Write-protect and Detection pins.
      * Add configuration of SPI devices.

Patch from Peer Georgi.

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