mt76x0: do not free/alloc buffers during suspend/resume

Do not free/alloc {tx,rx} buffers during suspend/resume phases
but use the ones previously allocated during hw probe.
Move {tx,rx}/mcu buffers allocation from mt76x0_init_hardware routine
to mt76x0_register_device

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>