sh: fixed PMB mode refactoring.

This introduces some much overdue chainsawing of the fixed PMB support.
fixed PMB was introduced initially to work around the fact that dynamic
PMB mode was relatively broken, though they were never intended to
converge. The main areas where there are differences are whether the
system is booted in 29-bit mode or 32-bit mode, and whether legacy
mappings are to be preserved. Any system booting in true 32-bit mode will
not care about legacy mappings, so these are roughly decoupled.

Regardless of the entry point, PMB and 32BIT are directly related as far
as the kernel is concerned, so we also switch back to having one select
the other.

With legacy mappings iterated through and applied in the initialization
path it's now possible to finally merge the two implementations and
permit dynamic remapping overtop of remaining entries regardless of
whether boot mappings are crafted by hand or inherited from the boot
loader.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/mm/Kconfig

@@ -80,30 +80,18 @@ config 32BIT
 	bool
 	default y if CPU_SH5
 
-config PMB_ENABLE
+config PMB
 	bool "Support 32-bit physical addressing through PMB"
 	depends on MMU && EXPERIMENTAL && CPU_SH4A && !CPU_SH4AL_DSP
+	select 32BIT
 	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
 	  29-bit physical addressing will be used.
 
-choice
-	prompt "PMB handling type"
-	depends on PMB_ENABLE
-	default PMB_FIXED
-
-config PMB
-	bool "PMB"
-	depends on MMU && EXPERIMENTAL && CPU_SH4A && !CPU_SH4AL_DSP
-	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
-	  29-bit physical addressing will be used.
-
-config PMB_FIXED
-	bool "fixed PMB"
-	depends on MMU && EXPERIMENTAL && CPU_SH4A && !CPU_SH4AL_DSP
+config PMB_LEGACY
+	bool "Support legacy boot mappings for PMB"
+	depends on PMB
 	select 32BIT
 	help
 	  If this option is enabled, fixed PMB mappings are inherited
@@ -111,8 +99,6 @@ config PMB_FIXED
 	  management. This is the closest to legacy 29-bit physical mode,
 	  and allows systems to support up to 512MiB of system memory.
 
-endchoice
-
 config X2TLB
 	bool "Enable extended TLB mode"
 	depends on (CPU_SHX2 || CPU_SHX3) && MMU && EXPERIMENTAL