setup correct int pipe type in ar9170_usb_exec_cmd

An int urb is constructed but we fill it in with a bulk pipe type.

Commit f661c6f8

 implemented a pipe type
check when CONFIG_USB_DEBUG is enabled. The check failed for all the ar9170
usb transfers and the driver could not configure the wifi dongle.

This went unnoticed until now because most people don't have
CONFIG_USB_DEBUG enabled.

Signed-off-by: Valentin Longchamp <valentin.longchamp@epfl.ch>
Cc: Stable <stable@kernel.org>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>