VkSamplerCreateInfo.magFilter and minFilter must match
VkSamplerYcbcrConversionCreateInfo.chromaFilter.

VkSamplerYcbcrConversionCreateInfo.chromaFilter is currently
hard-coded to VK_FILTER_NEAREST in
HardwareBufferImageSiblingVkAndroid(), so force magFilter and minFilter
to VK_FILTER_NEAREST in SamplerDesc::init() if an externalFormat is
being used.

Bug: b/178424566
Change-Id: Ia1f7fc21e3faa4e57f837ed3ae70608134150aea
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2683038
Commit-Queue: Tim Van Patten <timvp@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>