wifi: iwlwifi: fw: clean up PNVM loading code

This code is a bit of a maze of gotos etc. Clean up the
code a bit to make the intent clearer.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230606103519.51fb5ee63f21.I20f270b2d47612e84643dc235c2940b8d9ed9930@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>