The logic of PhysicalDevice::getImageFormatProperties(), as well as
testing with ANGLE, shows that multisampling of integer formats is
supported and works.  The value of
VkPhysicalDeviceLimits::sampledImageIntegerSampleCounts should therefore
be set to:

    VK_SAMPLE_COUNT_1_BIT | VK_SAMPLE_COUNT_4_BIT

Bug: b/147438583
Change-Id: Iaa7bd22789fd20b4e7975d3d2ffee2a8f90b006b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40068Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ian Elliott <ianelliott@google.com>