wifi: mt76: move leds struct in mt76_phy

Move leds struct in mt76_phy in order to have leds associated to phy
(e.g. in dbdc mode) instead of per device.

Tested-by: Frank Wunderlich <frank-w@public-files.de>
Co-developed-by: Ryder Lee <ryder.Lee@mediatek.com>
Signed-off-by: Ryder Lee <ryder.Lee@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>