[DebugInfo] Fix reading location tables of v5 units in DWP.

Without the patch, all version 5 compile units in a DWP file read
location tables from the beginning of a .debug_loclists.dwo section.
The patch fixes that by adjusting the reading offset the same way as
for pre-v5 units. The section identifier to find the contribution
entry corresponds to the version of the unit.

Differential revision: https://reviews.llvm.org/D77145