togari: Fix up navigation bar layout

Instead of using two dummy views to centre the keys, have the
centre LinearLayout use margins instead.

Change-Id: Ic7cdd171c0480048e73a7f1da49dc2e5514369e6
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_device_sony_togari into kk_mkt