ionic: only sync frag_len in first buffer of xdp

We don't want to try to sync more length than might be
in the first frag of an Rx skb, so make sure to use
the frag_len rather than the full len.

Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Link: https://lore.kernel.org/r/20240529000259.25775-7-shannon.nelson@amd.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>