UPSTREAM: bpf: sockmap, updating the sg structure should also update curr

[ Upstream commit bb9aefde5bbaf6c168c77ba635c155b4980c2287 ]

Curr pointer should be updated when the sg structure is shifted.

Fixes: 7246d8ed4dcce ("bpf: helper to pop data from messages")
Change-Id: I3c5d1dd94c2b874b6f0c34010f8e2a766f6081c1
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20231206232706.374377-3-john.fastabend@gmail.com


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