[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>

include/asm-arm/proc-fns.h

@@ -165,6 +165,8 @@
 
 #include <asm/memory.h>
 
+#ifdef CONFIG_MMU
+
 #define cpu_switch_mm(pgd,mm) cpu_do_switch_mm(virt_to_phys(pgd),mm)
 
 #define cpu_get_pgd()	\
@@ -176,6 +178,8 @@
 		(pgd_t *)phys_to_virt(pg);		\
 	})
 
+#endif
+
 #endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* __ASM_PROCFNS_H */