swapchain: Fix SHARED presentation modes

The code under the Vulkan swapchain code requires additional
images now, even though only one will be used for the SHARED
presentation modes.

Test: dEQP-VK.wsi.android.shared_presentable_image.scale_none.horizontal_mirror.inherit#continuous
Bug: 209035115
Bug: 200378297
Change-Id: Idbb3983becefa47e4f792106ab8274027a0db6c0