iwlwifi: mvm: consider d0i3_disable in iwl_mvm_is_d0i3_supported()

Consider the iwlwifi module param d0i3_disable when
considering whether d0i3 is supported.

(There is currently no need to differentiate between
supported and enabled, so keep the function as-is)

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