staging: ramster: Dont build ramster when CONFIGFS_FS=m

Ramster can't be a module (yet) and depends on CONFIGFS_FS=y, but
allmodconfig builds with CONFIGFS_FS=m, which breaks the build.
And forcing CONFIGFS_FS=y with select breaks the build in other ways.
So just don't build ramster unless CONFIGFS_FS=y.

Also, while we're here, add a comment as to why BROKEN is depended.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ramster/Kconfig

+# Dependency on CONFIG_BROKEN is because there is a commit dependency
+# on a cleancache naming change to be submitted by Konrad Wilk
+# a39c00ded70339603ffe1b0ffdf3ade85bcf009a "Merge branch 'stable/cleancache.v13'
+# into linux-next.  Once this commit is present, BROKEN can be removed
 config RAMSTER
 	bool "Cross-machine RAM capacity sharing, aka peer-to-peer tmem"
-	depends on (CLEANCACHE || FRONTSWAP) && CONFIGFS_FS && !ZCACHE && !XVMALLOC && !HIGHMEM && BROKEN
+	depends on (CLEANCACHE || FRONTSWAP) && CONFIGFS_FS=y && !ZCACHE && !XVMALLOC && !HIGHMEM && BROKEN
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
 	default n