eth: fbnic: Prefetch packet headers on Rx

Issue a prefetch for the start of the buffer on Rx to try to avoid cache
miss on packet headers.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20250813221319.3367670-5-mohsin.bashr@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>