wifi: iwlwifi: mvm: clarify EHT RU allocation bits

Calling this IWL_RX_PHY_DATA1_EHT_B0 is just confusing,
it's the RU allocation bit 0. Also then align the name
for B1-B7 accordingly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230531194629.824edb28c0eb.Ia9f74573e3ac771911b679558984f1bfb36de674@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>