init: export name_to_dev_t and mark name argument as const

DM will switch its device lookup code to using name_to_dev_t() so it
must be exported.  Also, the @name argument should be marked const.

Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/include/linux/mount.h b/include/linux/mount.h
index c2c561d..bca086d 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -92,6 +92,6 @@
 extern void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list);
 extern void mark_mounts_for_expiry(struct list_head *mounts);
 
-extern dev_t name_to_dev_t(char *name);
+extern dev_t name_to_dev_t(const char *name);
 
 #endif /* _LINUX_MOUNT_H */