Add kernel VARIANT_DEFCONFIG for GSM build

Change-Id: I895bedf10036628251d474a2de720390e454361e
Merge branch 'cm-10.1' of https://github.com/razrqcom-dev-team/android_device_motorola_xt925 into jb-mr1
Merge pull request #3 from pcarenza/jb-mr1

xt925 updartes