v3dv: fix Z coordinate for 3D blits

Reviewed-by: Alejandro PiƱeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7247>
diff --git a/src/broadcom/vulkan/v3dv_meta_copy.c b/src/broadcom/vulkan/v3dv_meta_copy.c
index 7c3bf36..22df8fc 100644
--- a/src/broadcom/vulkan/v3dv_meta_copy.c
+++ b/src/broadcom/vulkan/v3dv_meta_copy.c
@@ -4270,7 +4270,7 @@
          tex_coords[4] =
             !mirror_z ?
             (min_src_layer + (i + 0.5f) * src_z_step) / (float)src_level_d :
-            (max_dst_layer - (i + 0.5f) * src_z_step) / (float)src_level_d ;
+            (max_src_layer - (i + 0.5f) * src_z_step) / (float)src_level_d;
       }
 
       v3dv_CmdPushConstants(_cmd_buffer,