HW expects the data size in DUMP WQEs to be up to MTU.
Make sure they are in range.
We elevate the frag page refcount by 'n-1', in addition to the
one obtained in tx_sync_info_get(), having an overall of 'n'
references. We bulk increments by using a single page_ref_add()
command, to optimize perfermance.
The refcounts are released one by one, by the corresponding completions.