wifi: iwlwifi: Fix firmware version handling

wifi: iwlwifi: Fix firmware version handling

On my system the arithmetic done on the firmware numbers
results in a negative number, but since the types are
unsigned it gets interpreted as a large positive number.

The end result is that the firmware gets rejected and wifi
is defunct.

Switch to signed types to handle this case correctly.

iwlwifi 0000:0c:00.0: Driver unable to support your firmware API. Driver supports FW core 4294967294..2, firmware is 2.
iwlwifi 0000:0c:00.0: Direct firmware load for iwlwifi-5000-4.ucode failed with error -2
iwlwifi 0000:0c:00.0: Direct firmware load for iwlwifi-5000-3.ucode failed with error -2
iwlwifi 0000:0c:00.0: Direct firmware load for iwlwifi-5000-2.ucode failed with error -2
iwlwifi 0000:0c:00.0: Direct firmware load for iwlwifi-5000-1.ucode failed with error -2
iwlwifi 0000:0c:00.0: no suitable firmware found!
iwlwifi 0000:0c:00.0: minimum version required: iwlwifi-5000-1
iwlwifi 0000:0c:00.0: maximum version supported: iwlwifi-5000-5
iwlwifi 0000:0c:00.0: check git://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git

Cc: stable@vger.kernel.org
Fixes: 5f708cccde9d ("wifi: iwlwifi: add a new FW file numbering scheme")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220805
Link: https://patch.msgid.link/20251113222852.15896-1-ville.syrjala@linux.intel.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>