caif-hsi: robust frame aggregation for HSI

Implement aggregation algorithm, combining more data into a single
HSI transfer. 4 different traffic categories are supported:
 1. TC_PRIO_CONTROL .. TC_PRIO_MAX (CTL)
 2. TC_PRIO_INTERACTIVE            (VO)
 3. TC_PRIO_INTERACTIVE_BULK       (VI)
 4. TC_PRIO_BESTEFFORT, TC_PRIO_BULK, TC_PRIO_FILLER (BEBK)

Signed-off-by: Dmitry Tarnyagin <dmitry.tarnyagin@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>