iris: Enable PIPE_CAP_SURFACE_REINTERPRET_BLOCKS

iris: Enable PIPE_CAP_SURFACE_REINTERPRET_BLOCKS

This makes CompressedTexSubImage from a PBO source do proper GPU
rendering to upload instead of stalling to map the PBO source on
the CPU (then copying it on the CPU).

Thanks Bas Nieuwenhuizen for pointing out that Vulkan includes this
functionality, and to Jason Ekstrand for writing the code I adapted.
Vulkan only supports a single layer, however, and this code tries to
support multiple layers as long as it's miplevel 0.

Improves performance in Sid Meier's Civilization VI:

   Average frame time (ms):         -3.67423% +/- 1.46201% (n=5)
   99th percentile frame time (ms): -5.09910% +/- 3.87874% (n=5)