[Why]

DCN21 is stable enough to be build by default. So drop the flags.

[How]

Remove them using the unifdef tool. The following commands were executed
in sequence:

$ find -name '*.c' -exec unifdef -m -DCONFIG_DRM_AMD_DC_DCN2_1 -UCONFIG_TRIM_DRM_AMD_DC_DCN2_1 '{}' ';'
$ find -name '*.h' -exec unifdef -m -DCONFIG_DRM_AMD_DC_DCN2_1 -UCONFIG_TRIM_DRM_AMD_DC_DCN2_1 '{}' ';'

In addition:

* Remove from kconfig, and replace any dependencies with DCN1_0.
* Remove from any makefiles.
* Fix and cleanup Renoir definitions in dal_asic_id.h
* Expand DCN1 ifdef to include DCN21 code in the following files:
    * clk_mgr/clk_mgr.c: dc_clk_mgr_create()
    * core/dc_resources.c: dc_create_resource_pool()
    * gpio/hw_factory.c: dal_hw_factory_init()
    * gpio/hw_translate.c: dal_hw_translate_init()
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>