rds: Fix spelling mistakes

Fix some spelling mistakes in comments:
alloced  ==> allocated

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Link: https://lore.kernel.org/r/20210531063617.3018637-1-zhengyongjun3@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>