wifi: iwlwifi: mvm: clean up duplicated defines

VHT, HE and EHT rates use the same bits for NSS, so no need for
defines per PHY version.

Also use spatch to replace bit manipulation with FIELD_GET:

  @@
  identifier rate;
  @@
  -((rate & RATE_MCS_NSS_MSK) >> RATE_MCS_NSS_POS)
  +FIELD_GET(RATE_MCS_NSS_MSK, rate)

Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230305124407.167ed9477aa8.Ibd8e71d31896e8d8f067ce4e3a6e9a0e86c78f3f@changeid


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