defconfig: msm: Create symlinks for sdmsteppe defconfigs

Defconfigs are moved to vendor sub-directory. Create symlinks
for sdmsteppe defconfigs as necessary for userspace components
that are still hard-coded to the older location.

Change-Id: I99242c894afbab6ceeebc04789cb54fc15931671
Signed-off-by: Srinivas Ramana <sramana@codeaurora.org>