shader: remove unused function

This function was added but never used. Let's get rid of it.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Fixes: 5d2dde49 ("strings: move to 3 strings, and patch extensions onto end of string 0 (v2)")
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
7 jobs for remove-unused-function in 52 minutes and 55 seconds (queued for 46 minutes and 53 seconds)