net: libwx: handle page_pool_dev_alloc_pages error

In the Linux kernel, the following vulnerability has been resolved: net: libwx: handle page_pool_dev_alloc_pages error page_pool_dev_alloc_pages could return NULL. There was a WARN_ON(!page) but it would still proceed to use the NULL pointer and then crash. This is similar to commit 001ba0902046 ("net: fec: handle page_pool_dev_alloc_pages error"). This is found by our static analysis tool KNighter.