sispmctl: add comment mmu depends

Otherwise it shows up indirectly when toolchain options aren't enough
and then vanishes when they are fulfilled.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/sispmctl/Config.in

@@ -15,3 +15,4 @@ config BR2_PACKAGE_SISPMCTL
 
 comment "sispmctl needs a toolchain w/ threads, wchar"
 	depends on !BR2_TOOLCHAIN_HAS_THREADS || !BR2_USE_WCHAR
+	depends on BR2_USE_MMU