panfrost: delete stale editorconfig file
What does this MR do and why?
panfrost: delete stale editorconfig file
We no longer use 8-space indent in panfrost, so let's remove the needless .editorconfig, and instead inherit the 3-space indent from the toplevel .editorconfig.
Fixes: 0afd691f ("panfrost: clang-format the tree")