anv: Handle errors properly in anv_i915_query

DRM_IOCTL_I915_QUERY is a multi-query.  The most egregious errors are
returned via the usual ioctl error mechanism but there are also
per-query errors that are indicated by item.length < 0.  We need to
handle those as well.  While we're at it, scrape errno so we can return
a proper integer error.

Fixes: c0d07c838a "anv: Support i915 query (DRM_IOCTL_I915_QUERY)..."
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11770>

src/intel/vulkan/anv_gem.c

@@ -787,8 +787,13 @@ anv_i915_query(int fd, uint64_t query_id, void *buffer,
    };
 
    int ret = intel_ioctl(fd, DRM_IOCTL_I915_QUERY, &args);
+   if (ret != 0)
+      return -errno;
+   else if (item.length < 0)
+      return item.length;
+
    *buffer_len = item.length;
-   return ret;
+   return 0;
 }
 
 struct drm_i915_query_engine_info *
@@ -796,14 +801,14 @@ anv_gem_get_engine_info(int fd)
 {
    int32_t length = 0;
    int ret = anv_i915_query(fd, DRM_I915_QUERY_ENGINE_INFO, NULL, &length);
-   if (ret == -1)
+   if (ret < 0)
       return NULL;
 
    struct drm_i915_query_engine_info *info = calloc(1, length);
    ret = anv_i915_query(fd, DRM_I915_QUERY_ENGINE_INFO, info, &length);
    assert(ret == 0);
 
-   if (ret != 0) {
+   if (ret < 0) {
       free(info);
       return NULL;
    }