defconfig: msm8998: Enable kernel AIO support

New Android versions are using kernel AIO functionality for adb &
MTP interfaces for better performance. Hence enable CONFIG_AIO to
support same.

Change-Id: I8bfd6c631642f60390ee656e10d666766749f7b3
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>