CVE-2021-47483 regmap: Fix possible double-free in regcache_rbtree_exit()

In the Linux kernel, the following vulnerability has been resolved: regmap: Fix possible double-free in regcacherbtreeexit In regcacherbtreeinserttoblock, when 'present' realloc failed, the 'blk' which is supposed to assign to 'rbnode-block' will be freed, so 'rbnode-block' points a freed memory,...