MFC r309822, r310375

r309822:
[iwn] Perform BUS_DMASYNC_PREREAD when initializing RX buffer

BUS_DMASYNC_PREREAD is required when setting up RX buffer, otherwise
data provided by card can be overwritten by data evicted from cache

Also use proper tag when setting up RX descriptor

Reviewed by: adrian, avos, ivadasz
Differential Revision: https://reviews.freebsd.org/D8717

r310375:
[iwn] Several fixes for DMA part of iwn(4)

• Perform DMS sync when accessing/initializing ICT table
• Fix some DMA sync operations to use matching tags

Reviewed by: avos
Differential Revision: https://reviews.freebsd.org/D8804