mt76: mt7915: query station rx rate from firmware

When per-packet rate reporting is enabled, the hardware can get stuck under
some conditions. It self-recovers quickly, but in practice this leads to
reduced performance.
In order to avoid running into this issue, disable per-packet rate reporting
by default and query the rx rate from firmware instead, unless monitor mode
is enabled.

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