defconfig: Enable suspend support

After resolving the gpu related hard-hang with suspend/resume,
we can now safely enable suspend support in the hikey_defconfig

[conflict solved by Guodong]
hikey_defconfig is not used in this tree. Instead, move the
same change into arch/arm64/configs/defconfig

Change-Id: I169219d7eb669f9a1bddfe2e5d72c7d218a734e9
Signed-off-by: John Stultz <john.stultz@linaro.org>

Conflicts:
	arch/arm64/configs/hikey_defconfig
Signed-off-by: Guodong Xu <guodong.xu@linaro.org>