sh: New extended page flag to wire/unwire TLB entries

Provide a new extended page flag, _PAGE_WIRED and an SH4 implementation
for wiring TLB entries and use it in the fixmap code path so that we can
wire the fixmap TLB entry.

Signed-off-by: Matt Fleming <matt@console-pimps.org>
diff --git a/arch/sh/include/cpu-sh4/cpu/mmu_context.h b/arch/sh/include/cpu-sh4/cpu/mmu_context.h
index 3ce7ef6..03ea75c 100644
--- a/arch/sh/include/cpu-sh4/cpu/mmu_context.h
+++ b/arch/sh/include/cpu-sh4/cpu/mmu_context.h
@@ -25,6 +25,10 @@
 
 #define MMUCR_TI		(1<<2)
 
+#define MMUCR_URB		0x00FC0000
+#define MMUCR_URB_SHIFT		18
+#define MMUCR_URB_NENTRIES	64
+
 #if defined(CONFIG_32BIT) && defined(CONFIG_CPU_SUBTYPE_ST40)
 #define MMUCR_SE		(1 << 4)
 #else