mwifiex: copy AP's HT capability info correctly

While preparing association request, intersection of device's HT
capability information and corresponding fields advertised by AP
is used.

This patch fixes an error while copying this field from AP's
beacon.

Cc: <stable@vger.kernel.org>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>