galaxysmtd: board: update kernel defconfig filename

requires: https://gerrit.omnirom.org/8321/

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I0571ff8d68b65b92df8bae5dd84c77a8e3a91795
Merge branch 'android-4.4' of https://github.com/omnirom/android_device_samsung_galaxysmtd into HEAD