mtd: add leading underscore to all mtd functions

This patch renames all MTD functions by adding a "_" prefix:

mtd->erase -> mtd->_erase
mtd->read_oob -> mtd->_read_oob
...

The reason is that we are re-working the MTD API and from now on it is
an error to use MTD function pointers directly - we have a corresponding
API call for every pointer. By adding a leading "_" we achieve the following:

1. Make sure we convert every direct pointer users
2. A leading "_" suggests that this interface is internal and it becomes
   less likely that people will use them directly
3. Make sure all the out-of-tree modules stop compiling and the owners
   spot the big API change and amend them.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/lpddr/lpddr_cmds.c b/drivers/mtd/lpddr/lpddr_cmds.c
index 536bbce..fd19d3b 100644
--- a/drivers/mtd/lpddr/lpddr_cmds.c
+++ b/drivers/mtd/lpddr/lpddr_cmds.c
@@ -63,18 +63,18 @@
 	mtd->type = MTD_NORFLASH;
 
 	/* Fill in the default mtd operations */
-	mtd->read = lpddr_read;
+	mtd->_read = lpddr_read;
 	mtd->type = MTD_NORFLASH;
 	mtd->flags = MTD_CAP_NORFLASH;
 	mtd->flags &= ~MTD_BIT_WRITEABLE;
-	mtd->erase = lpddr_erase;
-	mtd->write = lpddr_write_buffers;
-	mtd->writev = lpddr_writev;
-	mtd->lock = lpddr_lock;
-	mtd->unlock = lpddr_unlock;
+	mtd->_erase = lpddr_erase;
+	mtd->_write = lpddr_write_buffers;
+	mtd->_writev = lpddr_writev;
+	mtd->_lock = lpddr_lock;
+	mtd->_unlock = lpddr_unlock;
 	if (map_is_linear(map)) {
-		mtd->point = lpddr_point;
-		mtd->unpoint = lpddr_unpoint;
+		mtd->_point = lpddr_point;
+		mtd->_unpoint = lpddr_unpoint;
 	}
 	mtd->size = 1 << lpddr->qinfo->DevSizeShift;
 	mtd->erasesize = 1 << lpddr->qinfo->UniformBlockSizeShift;