nfs: fix build error in nfsroot with initconst

fix build error with latest kbuild adjustments to initconst.

The commit a447c09 ("vfs: Use
const for kernel parser table") changed:

    static match_table_t __initdata tokens = {
to
    static match_table_t __initconst tokens = {

But the missing const causes popwerpc to fail with latest
updates to __initconst like this:

fs/nfs/nfsroot.c:400: error: __setup_str_nfs_root_setup causes a section type conflict
fs/nfs/nfsroot.c:400: error: __setup_str_nfs_root_setup causes a section type conflict

The bug is only present with kbuild-next.
Following patch has been build tested.

Signed-off-by: Sam Ravnborg <[email protected]>
Cc: Steven Whitehouse <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Acked-by: Jan Beulich <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>

fs/nfs/nfsroot.c

@@ -129,7 +129,7 @@ enum {
 	Opt_err
 };
 
-static match_table_t __initconst tokens = {
+static const match_table_t tokens __initconst = {
 	{Opt_port, "port=%u"},
 	{Opt_rsize, "rsize=%u"},
 	{Opt_wsize, "wsize=%u"},