sh: Flag PMB support as EXPERIMENTAL.

There's still work that needs to be done here, and this should not be
enabled by default on existing boards.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/mm/Kconfig b/arch/sh/mm/Kconfig
index f549b8c..5fd2184 100644
--- a/arch/sh/mm/Kconfig
+++ b/arch/sh/mm/Kconfig
@@ -59,7 +59,7 @@
 
 config PMB
 	bool "Support 32-bit physical addressing through PMB"
-	depends on MMU && (CPU_SUBTYPE_SH7780 || CPU_SUBTYPE_SH7785)
+	depends on MMU && EXPERIMENTAL && (CPU_SUBTYPE_SH7780 || CPU_SUBTYPE_SH7785)
 	select 32BIT
 	default y
 	help