drm/amdgpu: display/Kconfig: replace leading spaces with tab

This patch replace the leading spaces with tab, make them keep aligned with
the rest of the config options. No functional change.

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>