drm/amdkfd: Fix variable dereferenced before NULL check in 'kfd_dbg_trap_device_snapshot()'

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_debug.c:1024 kfd_dbg_trap_device_snapshot() warn: variable dereferenced before check 'entry_size' (see line 1021)

Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1018,12 +1018,14 @@ int kfd_dbg_trap_device_snapshot(struct kfd_process *target,
 		uint32_t *entry_size)
 {
 	struct kfd_dbg_device_info_entry device_info;
-	uint32_t tmp_entry_size = *entry_size, tmp_num_devices;
+	uint32_t tmp_entry_size, tmp_num_devices;
 	int i, r = 0;
 
 	if (!(target && user_info && number_of_device_infos && entry_size))
 		return -EINVAL;
 
+	tmp_entry_size = *entry_size;
+
 	tmp_num_devices = min_t(size_t, *number_of_device_infos, target->n_pdds);
 	*number_of_device_infos = target->n_pdds;
 	*entry_size = min_t(size_t, *entry_size, sizeof(device_info));