dm: Allow device removal features to be dropped

For SPL we don't expect to need to remove a device. Save some code space
by dropping this feature. The board config can define
CONFIG_DM_DEVICE_REMOVE if this is in fact needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@ti.com>

drivers/core/Makefile

@@ -4,5 +4,6 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-y := device.o lists.o root.o uclass.o util.o
+obj-$(CONFIG_DM)	+= device.o lists.o root.o uclass.o util.o
 obj-$(CONFIG_OF_CONTROL) += simple-bus.o
+obj-$(CONFIG_DM_DEVICE_REMOVE)	+= device-remove.o