lockd: move lockd's grace period handling into its own module

Currently, all of the grace period handling is part of lockd. Eventually
though we'd like to be able to build v4-only servers, at which point
we'll need to put all of this elsewhere.

Move the code itself into fs/nfs_common and have it build a grace.ko
module. Then, rejigger the Kconfig options so that both nfsd and lockd
enable it automatically.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
diff --git a/fs/nfs_common/Makefile b/fs/nfs_common/Makefile
index f689ed8..d153ca3 100644
--- a/fs/nfs_common/Makefile
+++ b/fs/nfs_common/Makefile
@@ -3,5 +3,6 @@
 #
 
 obj-$(CONFIG_NFS_ACL_SUPPORT) += nfs_acl.o
-
 nfs_acl-objs := nfsacl.o
+
+obj-$(CONFIG_GRACE_PERIOD) += grace.o