iwlwifi: pcie: indicate correct RB size to device

In the context info, we need to indicate the correct RB size
to the device so that it will not think we have 4k when we
only use 2k. This seems to not have caused any issues right
now, likely because the hardware no longer supports putting
multiple entries into a single RB, and practically all of
the entries should be smaller than 2k.

Nevertheless, it's a bug, and we must advertise the right
size to the device.

Note that right now we can only tell it 2k vs. 4k, so for
the cases where we have more, still use 4k. This needs to
be fixed by the firmware first.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Fixes: cfdc20ef ("iwlwifi: pcie: use partial pages if applicable")
Cc: stable@vger.kernel.org # v5.6
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20200417100405.ae6cd345764f.I0985c55223decf70182b9ef1d8edf4179f537853@changeid