Revert "Disable the xdp_umem_reg size check for now. (#1227)" (#1237)

This reverts commit e38d2af.

Author: arctic-alpaca

src/net/types.rs

@@ -1813,11 +1813,8 @@ fn test_sizes() {
     #[cfg(linux_kernel)]
     assert_eq_size!(UCred, libc::ucred);
 
-    // Linux added fields to `xdp_umem_reg` so it's bigger now.
-    /*
     #[cfg(target_os = "linux")]
     assert_eq_size!(super::xdp::XdpUmemReg, c::xdp_umem_reg);
-    */
     #[cfg(target_os = "linux")]
     assert_eq_size!(super::xdp::XdpOptions, c::xdp_options);
     #[cfg(target_os = "linux")]