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/docg3.c b/drivers/mtd/devices/docg3.c
index ad11ef0a..3746ae8 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -1820,12 +1820,12 @@
 	mtd->writesize = DOC_LAYOUT_PAGE_SIZE;
 	mtd->oobsize = DOC_LAYOUT_OOB_SIZE;
 	mtd->owner = THIS_MODULE;
-	mtd->erase = doc_erase;
-	mtd->read = doc_read;
-	mtd->write = doc_write;
-	mtd->read_oob = doc_read_oob;
-	mtd->write_oob = doc_write_oob;
-	mtd->block_isbad = doc_block_isbad;
+	mtd->_erase = doc_erase;
+	mtd->_read = doc_read;
+	mtd->_write = doc_write;
+	mtd->_read_oob = doc_read_oob;
+	mtd->_write_oob = doc_write_oob;
+	mtd->_block_isbad = doc_block_isbad;
 	mtd->ecclayout = &docg3_oobinfo;
 }