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>

include/config_defaults.h

@@ -20,4 +20,8 @@
 #define CONFIG_ZLIB 1
 #define CONFIG_PARTITIONS 1
 
+#ifndef CONFIG_SPL_BUILD
+#define CONFIG_DM_DEVICE_REMOVE
+#endif
+
 #endif