[PATCH] logfs: fix logfs build errors and dependencies

[Randy Dunlap <rdunlap@infradead.org>]

From: Randy Dunlap <rdunlap@infradead.org>

Fix build errors that happen when CONFIG_LOGFS=y and CONFIG_MTD=m:

fs/built-in.o: In function `logfs_mount':
super.c:(.text+0x92a6f): undefined reference to `logfs_get_sb_mtd'
fs/built-in.o: In function `logfs_get_sb_bdev':
(.text+0x93530): undefined reference to `logfs_get_sb_mtd'

This change allows CONFIG_BLOCK and CONFIG_MTD to be disabled, but
if either of them is enabled, CONFIG_LOGFS is limited (restricted) by
the setting of the former symbol(s).

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc:	Joern Engel <joern@logfs.org>
Cc:	Prasad Joshi <prasadjoshi.linux@gmail.com>
Cc:	logfs@logfs.org
---
 fs/logfs/Kconfig |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Found in linux-next but applies to mainline also.

--- linux-next-20160108.orig/fs/logfs/Kconfig
+++ linux-next-20160108/fs/logfs/Kconfig
@@ -1,6 +1,7 @@
 config LOGFS
 	tristate "LogFS file system"
-	depends on (MTD || BLOCK)
+	depends on BLOCK || BLOCK=n
+	depends on MTD || MTD=n
 	select ZLIB_INFLATE
 	select ZLIB_DEFLATE
 	select CRC32