drm: amdgpu: remove obsolete reference to config CHASH

Commit 04ed8459 ("drm/amdgpu: remove chash") removes the chash
architecture and its corresponding config CHASH.

There is still a reference to CHASH in the config DRM_AMDGPU in
./drivers/gpu/drm/Kconfig.

Remove this obsolete reference to config CHASH.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/Kconfig

@@ -256,7 +256,6 @@ config DRM_AMDGPU
 	select HWMON
 	select BACKLIGHT_CLASS_DEVICE
 	select INTERVAL_TREE
-	select CHASH
 	help
 	  Choose this option if you have a recent AMD Radeon graphics card.