drm/amdgpu: add Green_Sardine APU flag

Will be used for Green_Sardine which is a new APU.

Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/include/amd_shared.h

···
 	AMD_APU_IS_RAVEN2 = 0x00000002UL,
 	AMD_APU_IS_PICASSO = 0x00000004UL,
 	AMD_APU_IS_RENOIR = 0x00000008UL,
+	AMD_APU_IS_GREEN_SARDINE = 0x00000010UL,
 };
 
 /**