wifi: mt76: mt7915: fix unintended sign extension of mt7915_hw_queue_read()

In the expression "map[i].qid << 24" starts as u8, but is promoted to
"signed int", then sign-extended to type "unsigned long", which is not
intended. Cast to u32 to avoid the sign extension.

Fixes: 776ec4e7 ("mt76: mt7915: rework debugfs queue info")
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>