drm/amd: remove meaningless descending into amd/amdkfd/

Since commit 04d5e276 ("drm/amdgpu: Merge amdkfd into amdgpu"),
drivers/gpu/drm/amd/amdkfd/Makefile does not contain any syntax that
is understood by the build system.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/Makefile

@@ -63,7 +63,6 @@ obj-$(CONFIG_DRM_TTM)	+= ttm/
 obj-$(CONFIG_DRM_SCHED)	+= scheduler/
 obj-$(CONFIG_DRM_TDFX)	+= tdfx/
 obj-$(CONFIG_DRM_R128)	+= r128/
-obj-$(CONFIG_HSA_AMD) += amd/amdkfd/
 obj-$(CONFIG_DRM_RADEON)+= radeon/
 obj-$(CONFIG_DRM_AMDGPU)+= amd/amdgpu/
 obj-$(CONFIG_DRM_MGA)	+= mga/