NFS: Fix NFS KConfig typos

Two issues were noticed after the NFS v4.0 KConfig changes were merged
upstream. First, the text of CONFIG_NFS_V4 should not encourage people
to select it if they are unsure. Second, the new CONFIG_NFS_V4_0 option
should default to "on" instead of "off" to avoid breaking people's
setups if they are using NFS v4.0.

Reported-by: Niklas Cassel <cassel@kernel.org>
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Fixes: 4e02693525 ("NFS: Add a way to disable NFS v4.0 via KConfig")
Fixes: 7537db2480 ("NFS: Merge CONFIG_NFS_V4_1 with CONFIG_NFS_V4")
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

fs/nfs/Kconfig

@@ -87,7 +87,7 @@ config NFS_V4
 	  space programs which can be found in the Linux nfs-utils package,
 	  available from http://linux-nfs.org/.
 
-	  If unsure, say Y.
+	  If unsure, say N.
 
 config NFS_SWAP
 	bool "Provide swap over NFS support"
@@ -100,6 +100,7 @@ config NFS_SWAP
 config NFS_V4_0
 	bool "NFS client support for NFSv4.0"
 	depends on NFS_V4
+	default y
 	help
 	  This option enables support for minor version 0 of the NFSv4 protocol
 	  (RFC 3530) in the kernel's NFS client.