drm/amd/display: Fix Coverity INTEGER_OVERFLOW within dal_gpio_service_create

[Why]
For subtraction, coverity reports integer overflow
warning message when variable type is uint32_t.

[How]
Change variable type to int32_t.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/gpio/gpio_service.c

@@ -56,7 +56,7 @@ struct gpio_service *dal_gpio_service_create(
 	struct dc_context *ctx)
 {
 	struct gpio_service *service;
-	uint32_t index_of_id;
+	int32_t index_of_id;
 
 	service = kzalloc(sizeof(struct gpio_service), GFP_KERNEL);
 
@@ -112,7 +112,7 @@ struct gpio_service *dal_gpio_service_create(
 	return service;
 
 failure_2:
-	while (index_of_id) {
+	while (index_of_id > 0) {
 		--index_of_id;
 		kfree(service->busyness[index_of_id]);
 	}