staging: ft1000: fix error path

init_ft1000_netdev() calls kfree(netdev) instead of free_netdev(netdev).
It doesn't check kmalloc() return value.
ft1000_read_fifo_reg() doesn't free dr on error and calls kfree(urb)
instead of usb_free_urb(urb).  Also kfree(NULL) is OK.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>