drm/amdkfd: Fix variable set but not used warning

All warnings (new ones prefixed by >>):

   drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_svm.c: In function
'svm_range_deferred_list_work':
>> drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_svm.c:2067:22: warning:
variable 'p' set but not used [-Wunused-but-set-variable]
    2067 |  struct kfd_process *p;
         |

Fixes: 367c9b0f ("drm/amdkfd: Ensure mm remain valid in svm deferred_list work")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-By: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_svm.c

@@ -2066,13 +2066,10 @@ static void svm_range_deferred_list_work(struct work_struct *work)
 	struct svm_range_list *svms;
 	struct svm_range *prange;
 	struct mm_struct *mm;
-	struct kfd_process *p;
 
 	svms = container_of(work, struct svm_range_list, deferred_list_work);
 	pr_debug("enter svms 0x%p\n", svms);
 
-	p = container_of(svms, struct kfd_process, svms);
-
 	spin_lock(&svms->deferred_list_lock);
 	while (!list_empty(&svms->deferred_range_list)) {
 		prange = list_first_entry(&svms->deferred_range_list,