regmap: Remove dynamic allocation warnings for rbtree and maple

Thanks to Dan and Guenter's very prompt updates of the rbtree and maple
caches to support GPF_ATOMIC allocations and since the update shook out
a bunch of users at least some of whom have been suitably careful about
ensuring that the cache is prepoulated so there are no dynamic
allocations after init let's revert the warnings.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230721-regmap-enable-kmalloc-v1-1-f78287e794d3@kernel.org

Author: broonie

drivers/base/regmap/regmap.c

@@ -723,15 +723,6 @@ struct regmap *__regmap_init(struct device *dev,
 	} else {
 		if ((bus && bus->fast_io) ||
 		    config->fast_io) {
-			/*
-			 * fast_io is incompatible with REGCACHE_RBTREE and REGCACHE_MAPLE
-			 * since both need to dynamically allocate memory.
-			 */
-			if (config->cache_type == REGCACHE_RBTREE ||
-			    config->cache_type == REGCACHE_MAPLE) {
-				ret = -EINVAL;
-				goto err_name;
-			}
 			if (config->use_raw_spinlock) {
 				raw_spin_lock_init(&map->raw_spinlock);
 				map->lock = regmap_lock_raw_spinlock;