SUNRPC: sunrpc should not explicitly depend on NFS config options

Change explicit references to CONFIG_NFS_V4_1 to implicit ones
Get rid of the unnecessary defines in backchannel_rqst.c and
bc_svc.c: the Makefile takes care of those dependency.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/Kconfig

@@ -77,6 +77,7 @@ config NFS_V4
 config NFS_V4_1
 	bool "NFS client support for NFSv4.1 (EXPERIMENTAL)"
 	depends on NFS_FS && NFS_V4 && EXPERIMENTAL
+	select SUNRPC_BACKCHANNEL
 	select PNFS_FILE_LAYOUT
 	help
 	  This option enables support for minor version 1 of the NFSv4 protocol