iwlwifi: pcie: change 12k A-MSDU config to use 16k buffers

iwlwifi: pcie: change 12k A-MSDU config to use 16k buffers

If 12k A-MSDU size is requested, we will actually allocate 16k
due to page allocation. Thus, change it to actually mean 16k,
which is useful for certain sniffer use cases.

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.20201209231352.84ae405829d4.I31184f4be31f7c3feb9a29aef3a111e70d15c64a@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>