Removed redundant setup code from DSLFunction
Removed redundant setup code from DSLFunction

This code was written back when most of the function setup was happening
in IRGenerator (and therefore not being hit by the DSL, which was
creating a function declaration directly). Since then, the Function
setup code was moved from IRGenerator into SkSLFunctionDeclaration.cpp,
making this copy of it in the DSL redundant.

Change-Id: Ide110a4ae7dc8b3182c467ee3a2ca249b07d7e36
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/433159
Reviewed-by: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Commit-Queue: Ethan Nicholas <d2cfb8c2f603266f4dc3a6f09acbcc0089603b37@google.com>

google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia