btrfs: fix double free in create_space_info() error path

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix double free in create_space_info() error path

When kobject_init_and_add() fails, the call chain is:

create_space_info()

-> btrfs_sysfs_add_space_info_type()

-> kobject_init_and_add()

-> failure

-> kobject_put(&space_info->kobj)

-> space_info_release()

-> kfree(space_info)

Then control returns to create_space_info():

btrfs_sysfs_add_space_info_type() returns error

-> goto out_free

-> kfree(space_info)

This causes a double free.

Keep the direct kfree(space_info) for the earlier failure path, but

after btrfs_sysfs_add_space_info_type() has called kobject_put(), let

the kobject release callback handle the cleanup.