net: ethernet: mtk_eth_soc: fix misuse of mem alloc interface netdev[napi]_alloc_frag

net: ethernet: mtk_eth_soc: fix misuse of mem alloc interface netdev[napi]_alloc_frag

When rx_flag == MTK_RX_FLAGS_HWLRO,
rx_data_len = MTK_MAX_LRO_RX_LENGTH(4096 * 3) > PAGE_SIZE.
netdev_alloc_frag is for alloction of page fragment only.
Reference to other drivers and Documentation/vm/page_frags.rst

Branch to use __get_free_pages when ring->frag_size > PAGE_SIZE.

Signed-off-by: Chen Lin <chen45464546@163.com>
Link: https://lore.kernel.org/r/1654692413-2598-1-git-send-email-chen45464546@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>