wifi: iwlwifi: if scratch is ~0U, consider it a failure

We want to see bits being set in the scratch register upon resume, but
if all the bits are set, it means that we were kicked out of the PCI bus
and that clearly doesn't mean we can assume the firmware is still alive
after the suspend / resume cycle.

Fixes: cb347bd2 ("wifi: iwlwifi: mvm: fix hibernation")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250828095500.0f203e559242.I59eff718cb5fda575db41081a1a389f7af488717@changeid