Though the keyboard and other driver will continue to support the legacy
"gpio-key,wakeup", "linux,input-wakeup" boolean property to enable the
wakeup source, "wakeup-source" is the new standard binding.

This patch replaces all the legacy wakeup properties with the unified
"wakeup-source" property in order to avoid any futher copy-paste
duplication.

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>