fs: Add exofs to Kernel build

- Add exofs to fs/Kconfig under "menu 'Miscellaneous filesystems'"
- Add exofs to fs/Makefile

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/fs/Kconfig b/fs/Kconfig
index cef8b18..ae3b34a 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -169,6 +169,8 @@
 source "fs/sysv/Kconfig"
 source "fs/ufs/Kconfig"
 
+source "fs/exofs/Kconfig"
+
 endif # MISC_FILESYSTEMS
 
 menuconfig NETWORK_FILESYSTEMS