msm: kgsl: disable full cache flush if full_cache_threshold is 0
msm: kgsl: disable full cache flush if full_cache_threshold is 0

Make full_cache_threshold==0 mean never do a full cache flush,
since that is more useful than having it mean always do it.

Change-Id: I4ae46b6253f2d78a97f067b5f906637a3db1d5c8
Signed-off-by: Jeremy Gebben <b6cec76cbd1daeeb85b910c75fb55eadc32e8d1b@codeaurora.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas