iwlwifi: pcie: allocate much smaller byte-count table

The hardware needs a byte-count table with the size of each frame
on the queue to build A-MPDUs, but:
 * newer generation no longer have the duplicated space at the end,
   they can deal with the wrap properly - and we don't even fill
   the dup anyway
 * we have a maximum queue size of 512 right now and don't use the
   theoretical hardware maximum of 65536.

Together, this reduces the byte count table DMA allocation from
64KiB (65536*2 + 64*2 rounded up) to 1 KiB (though that might be
rounded up to a full 4 KiB page by the allocator, not sure it can
share the allocations.)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200425130140.c263b787b5ab.I059507a9760b1ce1d45d84dcaa91629a5cfb58e0@changeid