wil6210: fix max. MPDU size

When configuring Tx/Rx VRING's, driver need to specify max. MPDU size
It should take into account all overhead introduced by 802.3->208.11
transformation.

Change-Id: Icf0095825d100d9cab3152feaad7acaa8c12f3ab
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Git-commit: c44690a157719437d09c83eec393211e7fd65076
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-testing.git


Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>