evl: add explicit requirement for DEVTMPFS

We create devices on the fly as part of the procedure for
instantiating new EVL elements, expecting them to appear dynamically
in the /dev filesystem hierarchy.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

kernel/Kconfig.evl

@@ -7,6 +7,7 @@ menuconfig EVL
 	bool "EVL real-time core"
 	depends on HAVE_ARCH_EVL
 	select DOVETAIL
+	select DEVTMPFS
 	help
 
 	  The EVL core is a real-time component of the Linux kernel,