bonding: fix error checking in bond_debug_reregister()

bonding: fix error checking in bond_debug_reregister()

Since commit ff9fb72bc077 ("debugfs: return error values,
not NULL") changed return value of debugfs_rename() in
error cases from %NULL to %ERR_PTR(-ERROR), we should
also check error values instead of NULL.

Fixes: ff9fb72bc077 ("debugfs: return error values, not NULL")
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Link: https://lore.kernel.org/r/20230202093256.32458-1-zhengqi.arch@bytedance.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>