mwifiex: enable aggregation for TID 6 and 7 streams

Currently AMSDU and AMPDU aggregation is enabled for TID 0 to
TID 5 streams. Lets enable it for remaining two streams also.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>