net: ethernet: ti: am65-cpsw: fix memleak in certain XDP cases

In the Linux kernel, the following vulnerability has been resolved:

net: ethernet: ti: am65-cpsw: fix memleak in certain XDP cases

If the XDP program doesn't result in XDP_PASS then we leak the

memory allocated by am65_cpsw_build_skb().

It is pointless to allocate SKB memory before running the XDP

program as we would be wasting CPU cycles for cases other than XDP_PASS.

Move the SKB allocation after evaluating the XDP program result.

This fixes the memleak. A performance boost is seen for XDP_DROP test.

XDP_DROP test:

Before: 460256 rx/s 0 err/s

After: 784130 rx/s 0 err/s