Remove dead code from SPIR-V code generator.

These methods were not referenced anywhere.

Change-Id: Id56509b30335857d1e268bb4c9172127e296dce7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/758356
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2 files changed