Change the primary name of the extents feature to be 'extent'

This was the original name used by Lustre's patches; keep the plural
when converting feature names to a feature mask for compatibility's
sake.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/lib/e2p/feature.c b/lib/e2p/feature.c
index b3a2b4d..12cb8a3 100644
--- a/lib/e2p/feature.c
+++ b/lib/e2p/feature.c
@@ -62,11 +62,11 @@
 	{	E2P_FEATURE_INCOMPAT, EXT3_FEATURE_INCOMPAT_JOURNAL_DEV,
 			"journal_dev" },
 	{	E2P_FEATURE_INCOMPAT, EXT3_FEATURE_INCOMPAT_EXTENTS,
+			"extent" },
+	{	E2P_FEATURE_INCOMPAT, EXT3_FEATURE_INCOMPAT_EXTENTS,
 			"extents" },
 	{	E2P_FEATURE_INCOMPAT, EXT2_FEATURE_INCOMPAT_META_BG,
 			"meta_bg" },
-	{	E2P_FEATURE_INCOMPAT, EXT3_FEATURE_INCOMPAT_EXTENTS,
-			"extent" },
 	{	E2P_FEATURE_INCOMPAT, EXT4_FEATURE_INCOMPAT_64BIT,
 			"64bit" },
 	{       E2P_FEATURE_INCOMPAT, EXT4_FEATURE_INCOMPAT_FLEX_BG,