global_data.h: drop write-only field dm_root_f

The dm_root_f field seems to be entirely write-only and hence
redundant, unless 'git grep' fails to find some access generated via
preprocessor token concatenation or similar.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>

common/board_r.c

@@ -230,8 +230,7 @@ static int initr_dm(void)
 
 	oftree_reset();
 
-	/* Save the pre-reloc driver model and start a new one */
-	gd->dm_root_f = gd->dm_root;
+	/* Drop the pre-reloc driver model and start a new one */
 	gd->dm_root = NULL;
 #ifdef CONFIG_TIMER
 	gd->timer = NULL;

include/asm-generic/global_data.h

@@ -195,10 +195,6 @@ struct global_data {
 	 * @dm_root: root instance for Driver Model
 	 */
 	struct udevice *dm_root;
-	/**
-	 * @dm_root_f: pre-relocation root instance
-	 */
-	struct udevice *dm_root_f;
 	/**
 	 * @uclass_root_s:
 	 * head of core tree when uclasses are not in read-only memory.

test/dm/core.c

@@ -1006,7 +1006,6 @@ static int dm_test_uclass_before_ready(struct unit_test_state *uts)
 	ut_assertok(uclass_get(UCLASS_TEST, &uc));
 
 	gd->dm_root = NULL;
-	gd->dm_root_f = NULL;
 	memset(&gd->uclass_root, '\0', sizeof(gd->uclass_root));
 
 	ut_asserteq_ptr(NULL, uclass_find(UCLASS_TEST));