[ARM] nommu: adjust headers for !MMU ARM systems

Majorily based on Hyok Choi's patches, this fixes up the asm-arm
header files for mmuless systems.  Over and above Hyok's patches:

- nommu.h merged into mmu.h (it's only a structure)
- nommu_context.h is essentially the same as mmu_context.h, but
  without the MM switching code.

so there's no point having separate files.  Also, in memory.h,
there's no point #ifndef'ing PHYS_OFFSET and END_MEM - both
CONFIG_DRAM_BASE and CONFIG_DRAM_SIZE will always be set by the
configuration scripts.

Other files have minor formatting changes, but are essentially
the same.  Hyok's original patches were signed off thusly:

  Signed-off-by: Hyok S. Choi <hyok.choi@samsung.com>

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/include/asm-arm/mmu_context.h b/include/asm-arm/mmu_context.h
index 81c59fa..9fadb01 100644
--- a/include/asm-arm/mmu_context.h
+++ b/include/asm-arm/mmu_context.h
@@ -82,6 +82,7 @@
 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	  struct task_struct *tsk)
 {
+#ifdef CONFIG_MMU
 	unsigned int cpu = smp_processor_id();
 
 	if (prev != next) {
@@ -91,6 +92,7 @@
 		if (cache_is_vivt())
 			cpu_clear(cpu, prev->cpu_vm_mask);
 	}
+#endif
 }
 
 #define deactivate_mm(tsk,mm)	do { } while (0)