mt76x0: alloc mcu buffers first in mt76x0_mcu_cmd_init

swap mt76u_mcu_init_rx and mt76x0_mcu_function_select in
mt76x0_mcu_cmd_init routine in order to allocate mcu buffers
first and then send mcu commands

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>