[mlir] Remove filtering of deprecated rocm-agent-enumerator value gfx000 (llvm#166634)

Getting a gfx000 result from the `rocm-agent-enumerator` command was
deprecated beginning with the release of ROCm 7, but the MLIR build
system still filters it from results when looking for ROCm agents. This
PR removes that filtering.

There are a few other uses of "gfx000" in MLIR source, but those are
used as default options for running some passes, and, to my
understanding, have a semantically different meaning to the dummy result
returned from `rocm-agent-enumerator` and don't need to be changed.

Author: MixedMatched

mlir/lib/ExecutionEngine/CMakeLists.txt

@@ -354,7 +354,6 @@ if(LLVM_ENABLE_PIC)
       endif()
       string(STRIP AGENTS_STRING ${AGENTS_STRING})
       string(REPLACE "\n" ";" AGENTS_LIST ${AGENTS_STRING})
-      list(FILTER AGENTS_LIST EXCLUDE REGEX "gfx000")
       if (AGENTS_LIST STREQUAL "")
         message(SEND_ERROR "No non-CPU ROCm agents found on the system, and ROCM_TEST_CHIPSET is not defined")
       else()