RDMA/cma: Remove NULL check before dev_{put, hold}

RDMA/cma: Remove NULL check before dev_{put, hold}

The call netdev_{put, hold} of dev_{put, hold} will check NULL,
so there is no need to check before using dev_{put, hold},
remove it to silence the warnings:

./drivers/infiniband/core/cma.c:713:2-9: WARNING: NULL check before dev_{put, hold} functions is not needed.
./drivers/infiniband/core/cma.c:2433:2-9: WARNING: NULL check before dev_{put, hold} functions is not needed.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4668
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230331010633.63261-1-yang.lee@linux.alibaba.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>