stating/lustre: only build if configured as module

Lustre internal dependency needs to be cleaned up. Currently,
libcfs is acting as a basis of all other modules, while other
modules in lustre/ directory in turn depend on lnet modules.
It creates a dependency loop that need to be fixed. Hopefully
we will remove libcfs in the end. So just disable buildin for
now.
Signed-off-by: NPeng Tao <tao.peng@emc.com>
Signed-off-by: NAndreas Dilger <andreas.dilger@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/Kconfig

 config LUSTRE_FS
 	tristate "Lustre file system client support"
-	depends on STAGING && INET && BROKEN
+	depends on STAGING && INET && m && BROKEN
 	select LNET
 	select CRYPTO
 	select CRYPTO_CRC32