[ARM] 4615/4: sam926[13]ek buttons updated

From: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>

On the at92sam9263ek board, tell the input subsystem about the buttons.
This patch is taken from Andrew Victor's at91 patchset, then updated to
match the latest kernel code and to use labels printed on the board.

Also update the at91sam9261ek buttons to cope with input changes.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>