asm-generic/tlb: Guard with #ifdef CONFIG_MMU

The inner workings of the mmu_gather-based TLB invalidation mechanism
are not relevant to nommu configurations, so guard them with an #ifdef.
This allows us to implement future functions using static inlines
without breaking the build.
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

include/asm-generic/tlb.h

@@ -20,6 +20,8 @@
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 
+#ifdef CONFIG_MMU
+
 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
 /*
  * Semi RCU freeing of the page directories.
@@ -310,6 +312,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #endif
 #endif
 
+#endif /* CONFIG_MMU */
+
 #define tlb_migrate_finish(mm) do {} while (0)
 
 #endif /* _ASM_GENERIC__TLB_H */