drm/amdgpu: fix file permissions on some files

Drop execute.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/2085


Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>