defconfig: move vendor defconfigs to vendor/ subdirectory

Move all defconfigs down one level to vendor/.  Create symlinks as
necessary for userspace components that are still hard-coded to the
older location.

Change-Id: I98dac06f61eded8636912313122f90a8e93c6025
Signed-off-by: Vijaykumar Badiger <vbadig@codeaurora.org>