sh: Don't default enable PMB support.

This has the adverse effect of converting many 29bit configs to 32bit
mode, while this is a change that needs to be done manually for each
platform. Turn it off by default in order to cut down on spurious bug
reports.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/mm/Kconfig

@@ -83,7 +83,6 @@ config 32BIT
 config PMB_ENABLE
 	bool "Support 32-bit physical addressing through PMB"
 	depends on MMU && EXPERIMENTAL && CPU_SH4A && !CPU_SH4AL_DSP
-	default y
 	help
 	  If you say Y here, physical addressing will be extended to
 	  32-bits through the SH-4A PMB. If this is not set, legacy