mwifiex: remove warnings in mwifiex_cmd_append_11n_tlv()

Fix the following sparse warning in mwifiex_cmd_append_11n_tlv:

drivers/net/wireless/marvell/mwifiex/11n.c:358:65: warning: invalid assignment: &=
drivers/net/wireless/marvell/mwifiex/11n.c:358:65:    left side has type restricted __le16
drivers/net/wireless/marvell/mwifiex/11n.c:358:65:    right side has type int
drivers/net/wireless/marvell/mwifiex/11n.c:360:65: warning: invalid assignment: &=
drivers/net/wireless/marvell/mwifiex/11n.c:360:65:    left side has type restricted __le16
drivers/net/wireless/marvell/mwifiex/11n.c:360:65:    right side has type int
drivers/net/wireless/marvell/mwifiex/11n.c:366:65: warning: invalid assignment: &=
drivers/net/wireless/marvell/mwifiex/11n.c:366:65:    left side has type restricted __le16
drivers/net/wireless/marvell/mwifiex/11n.c:366:65:    right side has type int
drivers/net/wireless/marvell/mwifiex/11n.c:368:65: warning: invalid assignment: &=
drivers/net/wireless/marvell/mwifiex/11n.c:368:65:    left side has type restricted __le16
drivers/net/wireless/marvell/mwifiex/11n.c:368:65:    right side has type int

Fixes: 77423fa7

 ("mwifiex: fix incorrect ht capability problem")
Signed-off-by: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>