arm64: Enable OPP

Upstream OPP has been converted into a selectable symbol by commit
049d595a4db3b (PM / OPP: Make OPP invisible to users in Kconfig) however
for v3.10 it is less invasive to follow the practice in v3.10.

Signed-off-by: Mark Brown <broonie@linaro.org>
(cherry picked from LSK commit 4c9563dfc768f176de0c9cdf398ec8a108f374d0)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Conflicts:
	arch/arm64/Kconfig
1 file changed