RDMA/hns: fix inverted logic of readl read and shift

A previous change incorrectly changed the inverted logic and logically
negated the readl rather than the shifted readl result. Fix this by
adding in missing parentheses around the expression that needs to be
logically negated.

Addresses-Coverity: ("Logically dead code")
Fixes: 669cefb6

 ("RDMA/hns: Remove jiffies operation in disable interrupt context")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>