defconfig: Disable USER HELPHER Fallback for QCS405

For Thud upgrade system-udev is not supporting firmware loading from
user space, hence disabling user helper fallback config from kernel.

Change-Id: I746cb01d716297fcdbdb2acb55a6231a3f0c2ff3
Signed-off-by: Nagireddy Annem <nannem@codeaurora.org>