wil6210: 'length' in Tx/Rx descriptors is little endian

Hardware uses little endian for the Tx/Rx descriptors field 'length',
do appropriate conversions

Change-Id: I3385467eed062ec341ff183c81082310ff1a1bb0
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Git-commit: 7e594444448f221cff66a9309cbfd17430e463a0
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Liron Kuch <lkuch@codeaurora.org>