wifi: mt76: fix rx checksum offload on mt7615/mt7915/mt7921

Checking the relevant rxd bits for the checksum information only indicates
if the checksum verification was performed by the hardware and doesn't show
actual checksum errors. Checksum errors are indicated in the info field of
the DMA descriptor. Fix packets erroneously marked as CHECKSUM_UNNECESSARY
by checking the extra bits as well.
Those bits are only passed to the driver for MMIO devices at the moment, so
limit checksum offload to those.

Fixes: 2122dfbf ("mt76: mt7615: add rx checksum offload support")
Fixes: 94244d2e ("mt76: mt7915: add rx checksum offload support")
Fixes: 0e757327 ("mt76: mt7921: enable rx csum offload")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221005130824.23371-2-nbd@nbd.name