wifi: iwlwifi: mvm: remove setting of 'sta' parameter

cppcheck reports
[drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2686]: (warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?

The setting of the 'sta' parameter is not needed.  In the if-check that sets it
to NULL, mvm_sta is also set to NULL.  Then the next statement checks if
mvm_sta is NULL and does an early return. So remove setting sta.
Signed-off-by: NTom Rix <trix@redhat.com>
Signed-off-by: NGregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230314194113.711fe28cfdd6.I2f723f9d44f65720baaf3e84b72109759350a8f5@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/rs.c

@@ -2682,7 +2682,6 @@ static void rs_drv_get_rate(void *mvm_r, struct ieee80211_sta *sta,
 		/* if vif isn't initialized mvm doesn't know about
 		 * this station, so don't do anything with the it
 		 */
-		sta = NULL;
 		mvm_sta = NULL;
 	}