docs: nfsroot: Document that nfsvers=2 is the default

Nfsroot uses nfsvers=2 by default (as in fs/nfs/nfsroot.c), unlike is specified in a modern nfs man page. Document this.

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Hi all,

I just figured out that NFS v2 is the default version when mounting root over NFS. It'd be nice to tell in documentation this is actually the case.

Another option could be to change the default to something sensible. That would have potential for breaking something though. I wonder what others think.

 Documentation/filesystems/nfs/nfsroot.txt | 1 +
 1 file changed, 1 insertion(+)

index 5efae00f6c7f..5b1a5c5810a0 100644
@@ -66,6 +66,7 @@ nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
 
   <nfs-options>	Standard NFS options. All options are separated by commas.
 		The following defaults are used:
+			nfsvers		= 2
 			port		= as given by server portmap daemon
 			rsize		= 4096
 			wsize		= 4096

2.11.0