drm/amd/include:cleanup raven1 gc header files.

Cleanup asic_reg/raven1/GC folder. Remove unused files:
    gc_9_1_default.h  gc_9_1_sh_mask.h
Signed-off-by: NFeifei Xu <Feifei.Xu@amd.com>
Acked-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NJunwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/psp_v10_0.c

@@ -32,7 +32,7 @@
 
 #include "soc15ip.h"
 #include "raven1/MP/mp_10_0_offset.h"
-#include "raven1/GC/gc_9_1_offset.h"
+#include "gc/gc_9_1_offset.h"
 #include "sdma0/sdma0_4_1_offset.h"
 
 MODULE_FIRMWARE("amdgpu/raven_asd.bin");