defconfig: steppeauto: Set CONFIG_BLK_DEV_LOOP_MIN_COUNT to 16 for vts test

Set CONFIG_BLK_DEV_LOOP_MIN_COUNT=16 that pre-create loop
block devices at init time for vts_kernel_loopconfig_test.

Change-Id: Ie342467aa8208b367ca351d8989b7d166f6371e9
Signed-off-by: Vinay Sudra <vsudra@codeaurora.org>