nfsroot: Default mount option should ask for built-in NFS version

Change the nfsroot default mount option to ask for NFSv2 only *if* the
kernel was built with NFSv2 support.
If not, default to NFSv3 or as last choice to NFSv4, depending on actual
kernel config.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfsroot.c

@@ -88,7 +88,13 @@
 #define NFS_ROOT		"/tftpboot/%s"
 
 /* Default NFSROOT mount options. */
+#if defined(CONFIG_NFS_V2)
 #define NFS_DEF_OPTIONS		"vers=2,tcp,rsize=4096,wsize=4096"
+#elif defined(CONFIG_NFS_V3)
+#define NFS_DEF_OPTIONS		"vers=3,tcp,rsize=4096,wsize=4096"
+#else
+#define NFS_DEF_OPTIONS		"vers=4,tcp,rsize=4096,wsize=4096"
+#endif
 
 /* Parameters passed from the kernel command line */
 static char nfs_root_parms[NFS_MAXPATHLEN + 1] __initdata = "";