gpu: nvgpu: MISRA 14.4 err/ret/status as boolean

MISRA rule 14.4 doesn't allow the usage of integer types as booleans
in the controlling expression of an if statement or an iteration
statement

Fix violations where the integer variables err, ret, status are used
as booleans in the controlling expression of if and loop statements.

JIRA NVGPU-1019

Change-Id: Ia950828797b8eff4bc754269ea2d9fa272f59436
Signed-off-by: Amurthyreddy <amurthyreddy@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1919111
Reviewed-by: svc-misra-checker <svc-misra-checker@nvidia.com>
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: Scott Long <scottl@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/common/mm/nvgpu_allocator.c

@@ -164,7 +164,7 @@ int nvgpu_alloc_common_init(struct nvgpu_allocator *a, struct gk20a *g,
 	}
 
 	err = nvgpu_mutex_init(&a->lock);
-	if (err) {
+	if (err != 0) {
 		return err;
 	}