iwlwifi: make sure d3_suspend/resume ops exist

We added calls to d3_suspend/resume trans ops during the
suspend/resume flow.

However, the wrapper code didn't verify the trans ops were
actually defined, resulting in panic when they were not
(such as in the case of sdio trans)

Fixes: 6dfb36c8 ("iwlwifi: call d3_suspend/resume in d0i3 case as well")

Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>