drm/amdgpu: Move clocks closer to its only usage in amdgpu_parse_cg_state()

After commit 8020f0f9 ("drm/amd/amdgpu: enable W=1 for amdgpu"),
there is an instance of -Wunused-const-variable when CONFIG_DEBUG_FS is
disabled:

  drivers/gpu/drm/amd/amdgpu/../pm/amdgpu_pm.c:38:34: error: unused variable 'clocks' [-Werror,-Wunused-const-variable]
     38 | static const struct cg_flag_name clocks[] = {
        |                                  ^
  1 error generated.

clocks is only used when CONFIG_DEBUG_FS is set, so move the definition
into the CONFIG_DEBUG_FS block right above its only usage to clear up
the warning.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>