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>
diff --git a/common/board_r.c b/common/board_r.c
index c823cd2..d4ba245 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -230,8 +230,7 @@
 
 	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;
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index fcc3c6e..aa336d6 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -196,10 +196,6 @@
 	 */
 	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.
 	 *
diff --git a/test/dm/core.c b/test/dm/core.c
index 4741c81..dbad1b3 100644
--- a/test/dm/core.c
+++ b/test/dm/core.c
@@ -1006,7 +1006,6 @@
 	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));