mwifiex: remove extra padding to AMSDU

mwifiex: remove extra padding to AMSDU

Since commit: fb3c19bc9687d972b83faf366b38ac807eca8f25, adding
extra padding to AMSDU is redundant since same is being performed at
mwifiex_11n_aggregate_pkt after forming the AMSDU packet. Fixing it
by removing it.

Signed-off-by: Yogesh Ashok Powar <[email protected]>
Signed-off-by: Amitkumar Karwar <[email protected]>
Signed-off-by: Kiran Divekar <[email protected]>
Signed-off-by: Bing Zhao <[email protected]>
Signed-off-by: John W. Linville <[email protected]>