regmap: cache: Make regcache_sync_block_raw static

regcache_sync_block_raw is used only in this file. Hence make it static.
Silences the following warning:
drivers/base/regmap/regcache.c:608:5: warning:
symbol 'regcache_sync_block_raw' was not declared. Should it be static?
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache.c

@@ -605,7 +605,7 @@ static int regcache_sync_block_raw_flush(struct regmap *map, const void **data,
 	return ret;
 }
 
-int regcache_sync_block_raw(struct regmap *map, void *block,
+static int regcache_sync_block_raw(struct regmap *map, void *block,
 			    unsigned int block_base, unsigned int start,
 			    unsigned int end)
 {