Update Vulkan dEQP testing documentation.
Update Vulkan dEQP testing documentation.

SwiftShader can now be tested directly with dEQP, without using the
system's Vulkan loader or layers.

Bug b/116336664

Change-Id: I08816b5fb893d048c3dfe325ff54f44c646b250f
Reviewed-on: https://swiftshader-review.googlesource.com/c/22868
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>

bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader