defconfig: arm64: 8994: Enable the Operating Power Points library

The OPP library allows devices to be associated with
tables of data containing operating points (including
frequency and voltage).

Change-Id: I2b0a1524692401e7b459168b6bb3d67443441c68
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>