ieee80211: change HE nominal packet padding value defines

It's easier to use and understand, and to extend for EHT later,
if we use the values here instead of the shifted values.

Unfortunately, we need to add _POS so that we can use it in
places like iwlwifi/mvm where constants are needed.

While at it, fix the typo ("NOMIMAL") which also helps catch any
conflicts.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://lore.kernel.org/r/20211126104817.7c29a05b8eb5.I2ca9faf06e177e3035bec91e2ae53c2f91d41774@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>