qcacmn: Add NULL check while iterating sgl entries

__qdf_dma_get_sgtable_dma_addr() iterates through sgl entries
without appropriately checking for NULL pointers before attempting
to access them.

Fix the above-mentioned issue by adding a NULL check before access.

Change-Id: I7456db834f71b9b5cf3cb254526177b9fdcee664
CRs-Fixed: 2448239
1 file changed