vmxnet3: must split too big fragments

vmxnet3 has a 16Kbytes limit per tx descriptor, that happened to work
as long as we provided PAGE_SIZE fragments.

Our stack can now build larger fragments, so we need to split them to
the 16kbytes boundary.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: jongman heo <jongman.heo@samsung.com>
Tested-by: jongman heo <jongman.heo@samsung.com>
Cc: Shreyas Bhatewara <sbhatewara@vmware.com>
Reviewed-by: Bhavesh Davda <bhavesh@vmware.com>
Signed-off-by: Shreyas Bhatewara <sbhatewara@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>