dpaa2-switch: fix the error path in dpaa2_switch_rx()

In the Linux kernel, the following vulnerability has been resolved: dpaa2-switch: fix the error path in dpaa2_switch_rx() In case of an error in dpaa2_switch_rx(), the dpaa2_switch_free_fd() function is called in order to free the FD. This is incorrect since the dpaa2_switch_free_fd() is intended to be used on Tx frame descriptors, meaning that it expects in the software annotation area of the FD data to find a valid skb pointer on which to call dev_kfree_skb(). Fix this by extracting the dma_unmap_page() from dpaa2_switch_build_linear_skb() directly into the dpaa2_switch_rx() function. This allows us to directly use free_pages() in case of an error before an SKB was created and kfree_skb() afterwards.