rsi: rsi_91x_usb: Fix some basic kernel-doc issues

rsi: rsi_91x_usb: Fix some basic kernel-doc issues

Fixes the following W=1 kernel build warning(s):

 drivers/net/wireless/rsi/rsi_91x_usb.c:26: warning: cannot understand function prototype: 'u16 dev_oper_mode = DEV_OPMODE_STA_BT_DUAL; '
 drivers/net/wireless/rsi/rsi_91x_usb.c:88: warning: Function parameter or member 'endpoint' not described in 'rsi_write_multiple'
 drivers/net/wireless/rsi/rsi_91x_usb.c:88: warning: Excess function parameter 'addr' description in 'rsi_write_multiple'
 drivers/net/wireless/rsi/rsi_91x_usb.c:320: warning: Function parameter or member 'ep_num' not described in 'rsi_rx_urb_submit'
 drivers/net/wireless/rsi/rsi_91x_usb.c:320: warning: Function parameter or member 'mem_flags' not described in 'rsi_rx_urb_submit'

Cc: Amitkumar Karwar <amitkarwar@gmail.com>
Cc: Siva Rebbagondla <siva8118@gmail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201102112410.1049272-3-lee.jones@linaro.org