vfs: Use const for kernel parser table

This is a much better version of a previous patch to make the parser
tables constant. Rather than changing the typedef, we put the "const" in
all the various places where its required, allowing the __initconst
exception for nfsroot which was the cause of the previous trouble.

This was posted for review some time ago and I believe its been in -mm
since then.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Alexander Viro <aviro@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext4/super.c

@@ -919,7 +919,7 @@ enum {
 	Opt_inode_readahead_blks
 };
 
-static match_table_t tokens = {
+static const match_table_t tokens = {
 	{Opt_bsd_df, "bsddf"},
 	{Opt_minix_df, "minixdf"},
 	{Opt_grpid, "grpid"},