We already have the pointer available; no need to recompute it from the decorations.
This is groundwork for being able to index into arrays of storage image
descriptors correctly.

Bug: b/131082089
Change-Id: I574968b6ab8d205d5e4e3fcb4df5d08d2b88dcfa
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29568Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>