defconfig: msm: Disable EXT2 and EXT3 FS configs for MSM8998

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: I46aa9e9a9c7ebac4655f18fda1451bd2cf594a25
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>