scripts: gki: Fix setting of a CONFIG if it's unset in base defconfig

CONFIGs that are unset in base defconfig (# CONFIG_X is not set),
but gets enabled in fragments through menuconfig, the diff is shown
as: -# CONFIG_X is not set. However, for the fragments to work
correctly, it must be set to 'y'. Hence, explicitly set them in the
config fragments.

Change-Id: Ic1c1578fb8109c09f3f39b9d254474d2c341a6d6
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>