[roll] Roll fuchsia [fdf] Migrate mock-mmio-reg usages

Migrate the following mock-mmio-reg usages to
the forked SDK version:
- gdc_task_unittest
- ge2d_task_unittest
- registers-test
- ti-lp8556

Original-Bug: 382792202
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1172096
Original-Revision: 20d6582ca168d8f6b513ea223ab3de0eb8bc1dbc
GitOrigin-RevId: c515b4dc079d315fead314b96c864449a9e123b0
Change-Id: I73b5558d7d3bf8b47b96d4fac8d5c1c56f791566

Author: Sarah Chan

stem

@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="b044b0a07b6509e08cefbd035c9390e58e6b1b0c"/>
+             revision="20d6582ca168d8f6b513ea223ab3de0eb8bc1dbc"/>
   </projects>
   <hooks>
     <hook name="install-environment"