mt76: mt7915: fix endiannes warning mt7915_mcu_beacon_check_caps

Fix the following sparse warning mt7915_mcu_beacon_check_caps routine:
warning: cast to restricted __le32
warning: cast from restricted __le16

Fixes: 22dffbdd

 ("mt76: mt7915: introduce mt7915_mcu_beacon_check_caps()")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>