IB/hfi1: Remove redundant variable rcd

The variable rcd is being assigned a value from a calculation however the
variable is never read, so this redundant variable can be removed.

Cleans up the following clang-analyzer warning:

drivers/infiniband/hw/hfi1/affinity.c:986:3: warning: Value stored to
'rcd' is never read [clang-analyzer-deadcode.DeadStores].

Link: https://lore.kernel.org/r/1619346696-46300-1-git-send-email-jiapeng.chong@linux.alibaba.com
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>