Increase subPixelPrecisionBits from 4 to 8
Increase subPixelPrecisionBits from 4 to 8

This is a requirement of the Vulkan Roadmap 2022 profile. We've long
kept it at 4 sub-pixel precision bits because a significant number of
mobile devices report this number.

Test: dEQP-VK.api.info.profiles.roadmap_2022
Bug: b/226657516
Change-Id: Ifd95f44658590ff69ffe6d742186e3806c38bbfa
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/69451
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Kokoro-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>

google/swiftshader,google/swiftshader,google/swiftshader