wifi: iwlwifi: fw: allocate chained SG tables for dump

[ Upstream commit 7774e3920029398ad49dc848b23840593f14d515 ]

The firmware dumps can be pretty big, and since we use single
pages for each SG table entry, even the table itself may end
up being an order-5 allocation. Build chained tables so that
we need not allocate a higher-order table here.

This could be improved and cleaned up, e.g. by using the SG
pool code or simply kvmalloc(), but all of that would require
also updating the devcoredump first since that frees it all,
so we need to be more careful. SG pool might also run against
the CONFIG_ARCH_NO_SG_CHAIN limitation, which is irrelevant
here.

Also use _devcd_free_sgtable() for the error paths now, much
simpler especially since it's in two places now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250209143303.697c7a465ac9.Iea982df46b5c075bfb77ade36f187d99a70c63db@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>