ARM: 7935/1: sa1100: collie: add gpio-keys configuration

collie has several GPIO lines that act like keys - Sync/Wakeup button on
dock station is connected to GPIO line. Another one is connected to
on/off button. Add corresponding gpio-keys configuration.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>