linuxkpi: Add for_each_sgtable_dma_sg and for_each_sgtable_dma_page

Variants of for_each_sg/for_each_sg_dma_page but they operate on sgtable
structs.
Needed by drm v5.10

MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG

(cherry picked from commit 1aca8a6ec61cce1a4673a8f7b5412b106e366aff)