wifi: plfxlc: fix potential memory leak in __lf_x_usb_enable_rx()

urbs does not be freed in exception paths in __lf_x_usb_enable_rx().
That will trigger memory leak. To fix it, add kfree() for urbs within
"error" label. Compile tested only.

Fixes: 68d57a07

 ("wireless: add plfxlc driver for pureLiFi X, XL, XC devices")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221119051900.1192401-1-william.xuanziyang@huawei.com