mwifiex: fix wrong 11ac bits setting in fw_cap_info

commit 1e202242ee1432d68a8bea4919b2ae0ef19d9e06 upstream.

bit 14 is actually reserved and bit 12 & 13 should be used for
11ac capability in fw_cap_info.

Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>