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/lart.c b/drivers/mtd/devices/lart.c
index 3a11ea62..a595848 100644
--- a/drivers/mtd/devices/lart.c
+++ b/drivers/mtd/devices/lart.c
@@ -635,9 +635,9 @@
    mtd.erasesize = FLASH_BLOCKSIZE_MAIN;
    mtd.numeraseregions = ARRAY_SIZE(erase_regions);
    mtd.eraseregions = erase_regions;
-   mtd.erase = flash_erase;
-   mtd.read = flash_read;
-   mtd.write = flash_write;
+   mtd._erase = flash_erase;
+   mtd._read = flash_read;
+   mtd._write = flash_write;
    mtd.owner = THIS_MODULE;
 
 #ifdef LART_DEBUG