net/cxgb4: Fix referencing freed adapter

The adapter is freed before we check its flags. It was caused
by commit 144be3d ("net/cxgb4: Avoid disabling PCI device for
towice"). The problem was reported by Intel's "0-day" tool.

The patch fixes it to avoid reverting commit 144be3d. It's
responsing to bug#110450.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>