usb-linux: increase buffer for USB control requests

usb-linux: increase buffer for USB control requests

The WLAN USB stick ZyXEL NWD271N (0586:3417) uses very large
usb control transfers of more than 2048 bytes which won't fit
into the buffer of the ctrl_struct. This results in an error message
"husb: ctrl buffer too small" and a non-working device.
Increasing the buffer size to 8192 seems to be a safe choice.

Signed-off-by: Christian Krause <chkr@plauener.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>