sh: Disable 4KSTACKS on nommu.

4k stacks on nommu ends up blowing up with all sorts of interesting
slab corruption. Disable this by default unless BROKEN is also
enabled.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/Kconfig.debug

@@ -81,7 +81,7 @@ config DEBUG_STACK_USAGE
 
 config 4KSTACKS
 	bool "Use 4Kb for kernel stacks instead of 8Kb"
-	depends on DEBUG_KERNEL
+	depends on DEBUG_KERNEL && (MMU || BROKEN)
 	help
 	  If you say Y here the kernel will use a 4Kb stacksize for the
 	  kernel stack attached to each process/thread. This facilitates