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/phram.c b/drivers/mtd/devices/phram.c
index 23423bd..eff2b69 100644
--- a/drivers/mtd/devices/phram.c
+++ b/drivers/mtd/devices/phram.c
@@ -142,11 +142,11 @@
 	new->mtd.name = name;
 	new->mtd.size = len;
 	new->mtd.flags = MTD_CAP_RAM;
-        new->mtd.erase = phram_erase;
-	new->mtd.point = phram_point;
-	new->mtd.unpoint = phram_unpoint;
-	new->mtd.read = phram_read;
-	new->mtd.write = phram_write;
+	new->mtd._erase = phram_erase;
+	new->mtd._point = phram_point;
+	new->mtd._unpoint = phram_unpoint;
+	new->mtd._read = phram_read;
+	new->mtd._write = phram_write;
 	new->mtd.owner = THIS_MODULE;
 	new->mtd.type = MTD_RAM;
 	new->mtd.erasesize = PAGE_SIZE;