IB/core: Initialize sysfs attributes before sysfs create group

For dynamically allocated sysfs attributes there is a need to call
sysfs_attr_init in order to comply with lockdep, not calling it
will result in error complaining key is not in .data section.

Fixes: b40f4757 ("IB/core: Make device counter infrastructure dynamic")
Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>