Change UHID socket to be non-blocking

On some platforms, the logs indicate that the BTU task is stalled by
UHID driver when writing the HID descriptor to the kernel. This patch
converts the UHID socket to non-blocking to avoid stalling the main
BTU task.

Bug: 23978964
Change-Id: I5a7a3e106fb2c967d68f077faedcd4fe62bbd912