The list of SW descriptors that we create from the HW descriptors
in DP Tx completion path is corrupted in intra-bss path. This is causing a
crash when corrupted descriptor is accessed.
The cause of corruption seems to be due to incorrect rings being accessed.
Use cpu index to fetch tx. ring IDs.
Change-Id: I5342b7c4e24df983900fde79f36df8395bf628cb
CRs-Fixed: 3223420