drm/amdgpu: fix unsigned variable instance compared to less than zero

Currenly the error check on variable instance is always false because
it is a uint32_t type and this is never less than zero. Fix this by
making it an int type.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: 7d0e632 ("drm/amdgpu: update more sdma instances irq support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c

@@ -1963,7 +1963,8 @@ static int sdma_v4_0_process_ras_data_cb(struct amdgpu_device *adev,
 		struct ras_err_data *err_data,
 		struct amdgpu_iv_entry *entry)
 {
-	uint32_t instance, err_source;
+	uint32_t err_source;
+	int instance;
 
 	instance = sdma_v4_0_irq_id_to_seq(entry->client_id);
 	if (instance < 0)