ARM: dts: spear: replace gpio-key,wakeup with wakeup-source property

Keyboard driver for GPIO buttons(gpio-keys) checks for the legacy
"gpio-key,wakeup" boolean property to enable gpio buttons as wakeup
source.

Few dts files assign value "1" to gpio-key,wakeup which is incorrect.
Since the presence of the boolean property indicates it is enabled,
value of "0" or "1" have no significance.

This patch replaces the legacy "gpio-key,wakeup" with the unified
"wakeup-source" property which inturn fixes the above mentioned issue.

Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>