Vulkan: Fix two validation errors.

- Mipgen was only transitioning the first miplevel to GENERAL.
  Fix the image barrier helper function to transition all levels and
  layers.

- Validation layer was complaining that a VkSwapchainKHR was not
  properly destroyed. After recycling the swapchain, destroy the old
  one.

gfx/common/vulkan_common.c

@@ -950,8 +950,8 @@ void vulkan_image_layout_transition(
    barrier.dstQueueFamilyIndex         = VK_QUEUE_FAMILY_IGNORED;
    barrier.image                       = image;
    barrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
-   barrier.subresourceRange.levelCount = 1;
-   barrier.subresourceRange.layerCount = 1;
+   barrier.subresourceRange.levelCount = VK_REMAINING_MIP_LEVELS;
+   barrier.subresourceRange.layerCount = VK_REMAINING_ARRAY_LAYERS;
 
    vkCmdPipelineBarrier(cmd,
          srcStages,
@@ -2654,6 +2654,9 @@ bool vulkan_create_swapchain(gfx_ctx_vulkan_data_t *vk,
       return false;
    }
 
+   if (old_swapchain != VK_NULL_HANDLE)
+      vkDestroySwapchainKHR(vk->context.device, old_swapchain, NULL);
+
    vk->context.swapchain_width  = swapchain_size.width;
    vk->context.swapchain_height = swapchain_size.height;