wifi: bypass attribute lookup for max Ampdu and Amsdu sizes
Splitting this from MR !681 (merged) as it isn't directly related. Along with MR 681, should provide a 1.24x speedup on optimized test.py times.
test.py times
real 2m49.718s
user 33m37.859s
sys 0m58.930s
real 2m52.075s
user 33m34.395s
sys 1m1.929s
real 2m42.315s
user 33m36.812s
sys 0m58.762s
real 2m45.858s
user 33m33.441s
sys 1m0.059s