HID: thrustmaster: Fix memory leak in thrustmaster_interrupts()

thrustmaster_interrupts() does not free memory for send_buf when
usb_interrupt_msg() fails. This is fixed by the given patch.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>