defconfig: sdm670: 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: Ibb402e81a27fdc14d8f445a6a67390556b787c52
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>