iwlwifi: pcie: add new structure for Qu devices with medium latency

Some Qu devices require an intermediate amount of time to wake up and
for LTR notifications, so add a new structure with the correct values
for them and change the corresponding devices to use it.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200418110539.d6df2bcee78f.Ie008b0c8f03340a466c1ef981bfd25359c9de90d@changeid