wifi: mt76: Remove RCU section in mt7996_mac_sta_rc_work()

Since mt7996_mcu_add_rate_ctrl() and mt7996_mcu_set_fixed_field() can't
run in atomic context, move RCU critical section in
mt7996_mcu_add_rate_ctrl() and mt7996_mcu_set_fixed_field(). This patch
fixes a 'sleep while atomic' issue in mt7996_mac_sta_rc_work().

Fixes: 0762bdd3 ("wifi: mt76: mt7996: rework mt7996_mac_sta_rc_work to support MLO")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Tested-by: Ben Greear <greearb@candelatech.com>
Link: https://patch.msgid.link/20250605-mt7996-sleep-while-atomic-v1-5-d46d15f9203c@kernel.org


Signed-off-by: Felix Fietkau <nbd@nbd.name>