regmap: Unexport regcache_write() and regcache_read()

They have no current users which is fortunate as they don't take the lock
and therefore aren't safe to use externally. We'll need to add new
operations if direct cache access is needed.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache.c

@@ -211,7 +211,6 @@ int regcache_read(struct regmap *map,
 
 	return -EINVAL;
 }
-EXPORT_SYMBOL_GPL(regcache_read);
 
 /**
  * regcache_write: Set the value of a given register in the cache.
@@ -238,7 +237,6 @@ int regcache_write(struct regmap *map,
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(regcache_write);
 
 /**
  * regcache_sync: Sync the register cache with the hardware.