[Bluetooth]: Fix section mismatch of bt_sysfs_cleanup()

The bt_sysfs_cleanup() is marked with __exit attribute, but it will
be called from an __init function in the error case. So the __exit
attribute must be removed.

Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>