msm: kgsl: Fix conditional check for GMU_NONCACHED_USER

The conditional to initialize next_uncached_user_alloc is incorrect
and this patch simply fixes this.

Change-Id: I49c9aa5e2e84bf3c4855af6d166693683ce83c71
Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>