wifi: mt76: Assume __mt76_connac_mcu_alloc_sta_req runs in atomic context

wifi: mt76: Assume __mt76_connac_mcu_alloc_sta_req runs in atomic context

Rely on GFP_ATOMIC flag in __mt76_connac_mcu_alloc_sta_req since it can
run in atomic context. This is a preliminary patch to fix a 'sleep while
atomic' issue in mt7996_mac_sta_rc_work().

Fixes: 0762bdd30279 ("wifi: mt76: mt7996: rework mt7996_mac_sta_rc_work to support MLO")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250605-mt7996-sleep-while-atomic-v1-1-d46d15f9203c@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>