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/devices/spear_smi.c b/drivers/mtd/devices/spear_smi.c
index 0f0f1ac..5f42542 100644
--- a/drivers/mtd/devices/spear_smi.c
+++ b/drivers/mtd/devices/spear_smi.c
@@ -846,9 +846,9 @@
 	flash->mtd.erasesize = flash_devices[flash_index].sectorsize;
 	flash->page_size = flash_devices[flash_index].pagesize;
 	flash->erase_cmd = flash_devices[flash_index].erase_cmd;
-	flash->mtd.erase = spear_mtd_erase;
-	flash->mtd.read = spear_mtd_read;
-	flash->mtd.write = spear_mtd_write;
+	flash->mtd._erase = spear_mtd_erase;
+	flash->mtd._read = spear_mtd_read;
+	flash->mtd._write = spear_mtd_write;
 	flash->dev_id = flash_devices[flash_index].device_id;
 
 	dev_info(&dev->pdev->dev, "mtd .name=%s .size=%llx(%lluM)\n",