defconfig: msm: Disable EXT2 and EXT3 FS configs for MSM8996

This is required to fix the VTS test case failures which are failing
as the kernel supports EXT2/EXT3 but the tools mkfs.ext2/mkfs.ext3
doesn't exist anymore.

Change-Id: I433b3775c974a9bf38a62d9cd71319164fe0593f
Signed-off-by: Naitik Bharadiya <bharad@codeaurora.org>