MIPS: Probe cache line sizes once during boot

Rather than probing the cache line sizes on every call of any cache
maintenance function, probe them once during boot & store the values in
the global data structure for later use. This will reduce the overhead
of the cache maintenance functions, which isn't a big deal yet but
becomes more important once L2 caches which may expose their properties
via coprocessor 2 or the CM are supported.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

arch/mips/include/asm/cache.h

@@ -19,4 +19,13 @@
  */
 #define CONFIG_SYS_CACHELINE_SIZE ARCH_DMA_MINALIGN
 
+/**
+ * mips_cache_probe() - Probe the properties of the caches
+ *
+ * Call this to probe the properties such as line sizes of the caches
+ * present in the system, if any. This must be done before cache maintenance
+ * functions such as flush_cache may be called.
+ */
+void mips_cache_probe(void);
+
 #endif /* __MIPS_CACHE_H__ */