dm: sandbox: Switch over to using the new host uclass

Update the sandbox implementation to use UCLASS_HOST and adjust all
the pieces to continue to work:

- Update the 'host' command to use the new API
- Replace various uses of UCLASS_ROOT with UCLASS_HOST
- Disable test_eficonfig since it doesn't work (this should have a unit
  test to allow this to be debugged)
- Update the blk test to use the new API
- Drop the old header file

Unfortunately it does not seem to be possible to split this change up
further.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/dts/sandbox.dts

@@ -68,10 +68,6 @@
 		reg = <0x10002000 0x1000>;
 	};
 
-	host-fs {
-		compatible = "sandbox,bootdev-host";
-	};
-
 	i2c_0: i2c@0 {
 		#address-cells = <1>;
 		#size-cells = <0>;